Semiconductor Nanostructures

Deprocessing of Cu conductors with reliable electrical disconnect and without damage to underlying layers of the Integrated Circuits is critical for successful modification of ICs during FIB Circuit Edit. This presentation demonstrates performance of Cu line deprocessing achievable in existing 50KV and 30KV Ga FIB tools."

Cadmium sulfide (CdS) and cadmium telluride (CdTe) are two leading semiconductor materials used in the fabrication of thin film solar cells of relatively high power conversion efficiency and low manufacturing cost. Numerical simulations of current-voltage characteristics of thin film CdS/CdTe solar cell and nanowire CdS/CdTe solar cell were performed as a function of temperature using SCAPS-1D to demonstrate the fact that use of CdS nanowires enhances the efficiency of the CdS/CdTe solar cells. For the simulation of nanowire CdS/CdTe solar cell we changed some parameters (thickness, bandgap, electron and hole mobility) of the simulation of thin film CdS/CdTe solar cell. The Optical properties (absorption and scattering cross section) of CdS nanowire were observed to determine the preferable diameter for CdS nanowires. Simulations for realizing the absorption and scattering cross sections for various diameters of CdS nanowire were done using Lumerical FDTD solutions. From simulation results it was evident that nanowire CdS design was superior to planar CdS film due to enhanced performance in the CdS/CdTe solar cell through higher open circuit voltage and higher efficiency as for thin film CdS/CdTe solar cell the open circuit voltage was 0.6908V and efficiency was 14.15%. For nanowire CdS/CdTe solar cell model the open circuit voltage was 0.7889V and efficiency was 15.07%. Device parameters such as: thickness, bandgap, interface state density, density of states, electron and hole mobility, trap density, metal work function, temperature, parasitic series and shunt resistance were studied which can affect the efficiency of the nanowire-CdS/CdTe solar cell. The rollover effect on nanowire CdS/CdTe solar cell was explained by varying the majority carrier barrier height of back contact from 0.4 to 0.7 eV. It proves that change of barrier height at the contact can cause rollover effect. The crossover effect was observed by varying the thickness of CdS nanowire layer and removing defect of i-SnO2 layer. It was evident that the removal of defect in i-SnO2 is responsible for producing the crossover effect. Though SCAPS-1D is basically designed for simulation of thin film solar cells, it can be concluded that SCAPS-1D can also provide realistic simulation for nanowire CdS/CdTe solar cells.

Anatase TiO2 displaying dual morphologies were synthesized with a simple chemical route via a single step. A strong correlation between the dye sensitized solar cell (DSSC) device performance and the obtained dual morphologies are highlighted using relevant evidences from UV-vis and diffuse reflectance spectroscopy (DRS), Raman analysis, field emission scanning electron microscope, high resolution transmission electron microscope, current-voltage characteristics and impedance analysis. Structural investigation revealed that the interested medium in this work employed for the synthesis of TiO2 produced different types of dual morphologies such as nanospheres with nanoparticles (NSNP), microsphere decorated with nanoparticles (μSNP) and nanoparticles with stone like features (NPS). UV-vis and DRS results indicated the ability of the materials to assist with diffused reflectance and optical absorption of the screen printed photoanodes. In addition, an investigation of Raman vibrational characteristics was carried out in detail using synchronous and asynchronous 2D correlation analysis. The high intense Eg anatase mode of Raman spectrum was simulated using a phonon confinement model and its normalised spectra are compared with an experimental data. The resultant performances in the DSSCs were not indicative by the material properties; so, the charge transfer resistance (Rct) and recombination properties of the photoanode were investigated. These results showed that the Nyquist plot of NSNP possesses the smallest diameter, which reveals that the device based on NSNP offers the lowest Rct value that accounts for the higher conversion efficiencies when compared with the DSSC device based on photoanodes μSNP and NSP. It can be concluded that the improved power conversion efficiency shown by photoanode fabricated using NSNP has the dual role of optimum surface area for dye loading and light scattering centres. These properties, when optimized along with the offered pathway for electrolyte diffusion to the dye degeneration with less Rct, could lead to better photoelectric conversion efficiency.

The development of nanoparticle-based drugs has provided many opportunities to diagnose, treat and cure challenging diseases. Through the manipulation of size, morphology, surface modification, surface characteristics, and materials used, a variety of nanostructures can be developed into smart systems, encasing therapeutic and imaging agents with stealth properties. These nanostructures can deliver drugs to specific tissues or sites and provide controlled release therapy. This targeted and sustained drug delivery decreases the drug-related toxicity and increases the patient’s compliance with less frequent dosing. Nanotechnology employing nanostructures as a tool has provided advances in the diagnostic testing of diseases and cure. This technology has proven beneficial in the treatment of cancer, AIDS, and many other diseases. This review article highlights the recent advances in nanostructures and nanotechnology for drug delivery, nanomedicine and cures.

Both the origins of the high open circuit voltages (VOC) in amorphous silicon solar cells having p layers prepared with very high hydrogen dilution and the physical structure of these optimum p layers remain poorly understood topics, with several studies offering conflicting views. This work attempts to overcome the limitations of previous studies by combining insights available from electronic measurements, real time spectroscopic ellipsometry, atomic force microscopy, and both high-resolution transmission electron microscopy (TEM) and dark field TEM of cross sections of entire solar cells. It is found that solar cells fabricated with p layers having a low volume fraction of nanocrystals embedded in a protocrystalline Si:H matrix possess lower recombination at the i/p interface than standard cells and deliver a higher VOC. The growth of the p layers follows a thickness evolution in which pure protocrystalline character is observed at the interface to the i layer. However, a low density of nanocrystallites nucleates with increasing thickness. The advantages offered by the protocrystalline character associated with the amorphous phase of the mixed-phase (amorphous+nanocrystalline) p layers prepared with excess H2 dilution account for the improved VOC of the optimum p layers. In this model, the appearance of a low volume fraction of nanocrystals near the top transparent conductor interface is proposed to be incidental to the high VOC.

In this review we describe some new approaches
in the surface photovoltage spectroscopy (SPS)
performed in the metal-insulator-semiconductor
operation mode, which are related to open questions
in the SPS characterization of nanostructures. The
first new approach is based on surface photovoltage
(SPV) phase spectroscopy. We show that i) the
sign of the bandgap-related knee in the spectrum of the SPV phase modulus is positive (negative)
for downward (upward) surface band bending and
ii) for the case of non-linear recombination, the
SPV phase spectrum reflects the features of
the optical absorption coefficient spectrum. We
demonstrate the necessity of simultaneous
examination of both amplitude and phase SPV
spectra in order to understand correctly the
experimental data. As a second original approach,
we have developed a vector model, in which the
SPV signal is represented by a radial vector,
containing all the information given by the
amplitude and phase SPV spectra. Further, after a
brief overview of the SPS characterization of
nanostructures in the last decade, we present the
results of our pioneering SPS studies of various
nanostructures with graded interfaces including
AlAs/GaAs superlattices with GaAs embedded
quantum wells, multilayer InAs/InP quantum
wires, InAs/InGaAlAs quantum dashes-in-well
laser structures and multilayer InP/GaAs type II
quantum dots. The interpretation of the amplitude
and phase SPV spectra is carried our by the
proposed vector model for the SPV signal in
parallel with the analysis of data obtained by other
experimental methods and electronic structure
calculations. As a result valuable information
about the investigated systems is obtained.

In recent years, II–VI semiconductors have been the focus of intense research and development due to their potential use in various applications. II–VI semiconductors are compound semiconductors formed by group IIB metallic elements (Cd, Zn, and Hg) with group VI nonmetallic elements (O, S, Se, and Te). Among such compounds,
cadmium sulfide (CdS) has been of keen interest due to its extraordinary
optoelectronic properties which has led to unique device applications in thin-film photovoltaics [1, 2], nanophotodetectors [3], lasers, etc. Zinc oxide (ZnO) is another important II–VI semiconductor with exceptionally good properties and wide applications in varistors, phosphors, sensors, and optoelectronic devices [4–6]. In this chapter, we describe the basic properties of CdS, ZnO, and related materials and their processing techniques, both in thin-film and nanostructured forms. A detailed description of the preparation methods, morphologies and optoelectronic properties is presented.
In this section, important growth techniques, properties, and applications of CdS and related ternary and quaternary compounds are described, beginning with those of CdS.

Vanadium pentoxide (V2O5) thin films were deposited on glass substrates using spray pyrolysis technique. Aqueous solution of ammonium vanadate with 0.1 M concentration was used to deposit V2O5 thin films at different substrate temperatures. The structural, morphological, electrical, optical and vapour sensing properties of the films were investigated. XRD patterns confirmed the polycrystalline nature of the films with orthorhombic structure. Crystallite size was increased with an increase in the substrate temperature. SEM images showed the formation of films with flower like morphology. From the optical absorbance spectra, the optical band gap was determined and varied between 3.34 to 3.24 eV. The charge carrier concentration was found to be increased with substrate temperature. Room temperature xylene sensing characteristics of the films were investigated. The influence of substrate temperature on the vapour sensing characteristics of V2O5 is reported.

In this paper, the potential distribution for symmetric double gate stack-oxide junctionless field effect transistor (DGS-JLFET) in subthreshold region has been observed. Using the potential distribution, current vs voltage (Ids vs. Vgs) characteristic and various short channel effects such as on-off ratio (Ion/Ioff), subthreshold swing (SS), drain induced barrier lowering (DIBL), threshold voltage roll-off (TVRO) have been studied by changing device parameters. It has been observed that, if the dielectric constant of high-k oxide is increased and the thickness of stack-oxide is decreased, device shows better short channel effect (SCE) performance in the most of the cases. Keywords— Double gate stack-oxide junctionless field effect transistor (DGS-JLFET), on current (Ion), off current (Ioff), on-off ratio (Ion/Ioff), subthreshold swing (SS), drain induced barrier lowering (DIBL), threshold voltage roll-off (TVRO), short channel effect (SCE).

The heteroepitaxial growth of the new ternary, group-IV, semiconductor material, Si1-x-yGexCy on Si(100), has been investigated. The epitaxial quality of Si1-x-yGexCy is found to be inferior to that of Si1-xGex with similar Si/Ge concentration ratio, grown under identical conditions, and the quality deteriorates with increasing C fraction. Also, the surface roughness, as studied by tapping mode atomic force microscopy, increases with increasing C fraction as well as with increasing Ge fraction, suggesting a transition from Frank-van der Merve to Stranski-Krastanov type growth. We suggest that the very large mismatch between the average bond length in the Si1-x-yGexCy material, as determined by Vegard's law, and the equilibrium Si-C bond length, weakens the Si-C bonds and reduces the elastic range of the material, thus lowering the barrier for dislocation and stacking fault formation. The change in elasticity may also be responsible for the change in growth morphology, either directly by a lowered barrier for island formation or indirectly through the formation of defects. A decrease in Ge incorporation in the Si1-x-yGexCy films with increasing C incorporation suggests a repulsive Ge-C interaction. Moreover, we observe a C-rich, Ge-deficient precursor phase to SiC precipitates at a growth temperature of 560 degrees C, whereas at 450 degrees C no such phase can be observed. The temperature dependence of the precursor formation is consistent with C bulk diffusion. Infrared absorption measurements cannot be used to detect the precursor phase. Finally, the onset of epitaxial breakdown is discussed and an accurate and independent determination of the C fraction and its substitutionality is emphasized. (

In order to see effects of interfacial (with and without different graphene (GP) + Ca1.9Pr0.1Co4Ox-doped PVA) layer on the electrical characteristics of conventional Au/n-Si (MS) contacts. Therefore, Au/(GP + Ca1.9Pr0.1Co4Ox-doped PVA)/n-Si (MPS) structures were fabricated with different rates of (%3 GP, %7 GP) PVA and were fabricated on same n-Si wafer. Au/n-Si (MS), Au/PVA/n-Si, Au/%3GP + Ca1.9Pr0.1Co4Ox-doped PVA/n-Si and Au/%7GP + Ca1.9Pr0.1Co4Ox-doped PVA/n-Si structures were fabricated and their main electrical characteristics compared each other by using current–voltage (I–V) methods. The forward and reverse bias current voltage (I–V) characteristics of with and without GP + Ca1.9Pr0.1Co4Ox-doped PVA/n-Si at room temperature were studied to investigate its main electrical parameters. The energy density distribution profile of the interface states (Nss) was obtained from the forward bias I–V data by taking into account voltage dependent ideality factor (n(v)) and effective barrier height (Φe) and they increase from at about mid-gap energy of Si to bottom of conductance band edge. In addition, voltage dependent profile of resistivity of the structure was obtained from I–V data for four different structures. The analysis of experimental results reveals that the existence of GP + Ca1.9Pr0.1Co4Ox-doped PVA interfacial layer improves the performance of MS structure. In order to determine the dominant current-transport mechanism (CTM) in the whole forward bias region of these structures, the double logarithmic forward bias I–V plots were also drawn. These plots exhibit two distinct linear region with different slopes which are corresponding to intermediate and high forward bias voltages. The slope of these plots show that in the region 1 (low biases) the dominant CTM is trap-charge-limited current (TCLC), whereas in the region 2 (high biases) is space-charge-limited current (SCLC) for four diodes.

This research was funded by, and implemented within, a UK national research organisation, while the author was the KE and Impact Evaluation Manager responsible for assessing impact on a £15m UK government-funded research programme.

This work was also submitted as the authors MBA dissertation which was accepted and awarded in 2009.

ABSTRACT: A methodology and methods ‘toolbox’ is proposed for conducting impact research and assessment from within research programmes. The emphasis is upon how to clarify and assess the wider impacts from the early stages onwards.

The approach explicitly acknowledges, and attempts to address, the known issues and challenges of impact assessment while drawing upon the resources and opportunities available to research managers and researchers within such programmes.

The study has two triangulating foundations. Firstly, it examines the academic literature to help identify and design the pilot methodology and methods. Secondly it trials these in a real programme to both test and improve them.

The study was conducted over one year within one leading UK research organisation, where two research programmes (and around 60 research projects of £15m total value) were being assessed for their impacts. The study draws upon actual impact management experience and reflection, prospective (ex ante) and retrospective (ex post) assessments, participatory contributions from leading researchers undergoing assessment, and consultation with external users. The findings of this study outline the pilot and its first iteration. Recommendations are made for improvement to the methodology and methods.

A subsequent follow-on bid to UK government incorporating the impacts identified from implementing this methodology, successfully led to a further £15m of government funding.

It is expected the pilot methodology and methods will be applicable to other organisations, conducting and funding such research programmes, required to research and assess the wider research impacts.

Although primary focus of implemetation trials was upon research in physical sciences, technology, high-tech engineering, computing/IT, and environment, the wider literature study, the methodology design and justification, the methods proposed and used, and the resulting general recommendations and lessons are expected to apply more broadly to many other research areas, where the impact is to be found more widely in the society, economy, government or public sector or within organizations, policies, professions or the public.

Interest in this work is expected from research programme managers, impact managers and assessors, management consultants advising in this area, and government funding managers, all seeking to embed a developing approach to understand, capture, and enhance wider impact.

Four-dimensional ultrafast electron microscopy (4D-UEM) is a novel analytical technique that aims to fulfill the long-held dream of researchers to investigate materials at extremely short spatial and temporal resolutions by integrating the excellent spatial resolution of electron microscopes with the temporal resolution of ultrafast femtosecond laser-based spectroscopy. The ingenious use of pulsed photoelectrons to probe surfaces and volumes of materials enables time-resolved snapshots of the dynamics to be captured in a way hitherto impossible by other conventional techniques. The flexibility of 4D-UEM lies in the fact that it can be used in both the scanning (S-UEM) and transmission (UEM) modes depending upon the type of electron microscope involved. While UEM can be employed to monitor elementary structural changes and phase transitions in samples using real-space mapping, diffraction, electron energy-loss spectroscopy, and tomography, S-UEM is well suited to map ultrafast dynamical events on materials surfaces in space and time. This review provides an overview of the unique features that distinguish these techniques and also illustrates the applications of both S-UEM and UEM to a multitude of problems relevant to materials science and chemistry.

The population of all non-equilibrium lattice defects in materials is referred to as microstructure. Examples are point defects such as substitutional and interstitial atoms, and vacancies; line defects such as dislocations; planar defects such as interfaces and stacking faults; or mesoscopic defects such as second-phase precipitates. These types of lattice imperfections are usually described in terms of their structural features, breaking the periodicity of the otherwise regular crystalline structure. Recent analytical probing at the nanoscale has revealed that their chemical features are likewise important and characteristic. The structure of the defects as well as their individual chemical composition, that is their chemical decoration state, which results from elemental partitioning with the adjacent matrix, can significantly influence the electrical and thermal transport properties of thermoelectric materials. The emergence of atom probe tomography (APT) has now made routinely accessible the mapping of three-dimensional chemical composition with sub-nanometer spatial accuracy and elemental sensitivity in the range of tens of ppm. Here, we review APT-based investigations and results related to the local chemical decoration states of various types of lattice defects in thermoelectric materials. APT allows to better understand the interplay between thermoelectric properties and microstructural features, extending the concept of defect engineering to the field of segregation engineering so as to guide the rational design of high-performance thermoelectric materials.

The dielectric properties of Au/(1 % graphene
doped-Ca1.9Pr0.1Co4Ox)/n-Si structures were investigated
by the impedance spectroscopy method including capacitance–
voltage (C–V) and conductance–voltage (G/x–
V) measurements in the frequency range of 10–2 MHz at
room temperature. The experimental results show that the
real and imaginary parts of dielectric constant (e0, e00) and
electric modulus (M0 andM00), and ac electrical conductivity
(rac) are a strong functions of frequency and voltage, both.
Negative dielectric constant behavior was observed at sufficiently
high forward bias voltages at low frequencies and it
was attributed to the interfacial polarization, interface traps
and series resistance. e0 decreases with increasing frequency
at sufficiently high biases whereas e00 increases. Since
interfacial polarization and interface states, both, can follow
the ac external signal easily at low frequencies, there occurs
a contribution to the measured capacitance and conductance.
The negative values of e0 correspond to maximum value of
e00. Such contrary behavior in the e0 and e00 appears as an
abnormality when compared to the conventional behavior
metal–semiconductor structures with and without interfacial
layer. Experimental results confirmed that the dielectric
properties of these structures are quite sensitive to the frequency and applied bias voltage, both, especially at low
frequencies and high voltages because of density distribution
of interface states and interfacial polarization.

Current–voltage (I–V) characteristics of Au/PVA/n-Si (1 1 1) Schottky barrier diodes (SBDs) have been investigated in the temperature range 80–400 K. Here, polyvinyl alcohol (PVA) has been used as interfacial layer between metal and semiconductor layers. The zero-bias barrier height (ΦB0) and ideality factor (n) determined from the forward bias I–V characteristics were found strongly dependent on temperature. The forward bias semi-logarithmic I–V curves for different temperatures have an almost common cross-point at a certain bias voltage. The values of ΦB0 increase with the increasing temperature whereas those of n decrease. Therefore, we have attempted to draw ΦB0 vs. q/2kT plot in order to obtain evidence of a Gaussian distribution (GD) of the barrier heights (BHs). The mean value of BH and standard deviation (σ0) were found to be 0.974 eV and 0.101 V from this plot, respectively. Thus, the slope and intercept of modified vs. q/kT plot give the values of and Richardson constant (A⁎) as 0.966 eV and 118.75 A/cm2K2, respectively, without using the temperature coefficient of the BH. This value of A* 118.75 A/cm2K2 is very close to the theoretical value of 120 A/cm2K2 for n-type Si. Hence, it has been concluded that the temperature dependence of the forward I–V characteristics of Au/PVA/n-Si (1 1 1) SBDs can be successfully explained on the basis of the Thermionic Emission (TE) theory with a GD of the BHs at Au/n-Si interface.

"WET NANO-BONDING OF SILICA-TO-SI AND SILICA-TO-SILICA BELOW 200°C  BY H2O CATALYSIS AND A 2-D PRECURSOR PHASE:
TMAFM, HYDROAFFINITY AND SURFACE FREE ENERGY ANALYSIS

R. Bennett-Kennett*, S. D. Whaley, N. Herbots*, C. F. Watson*, R.J. Culbertson, A. Murphy,* S. Farmer,** P. Rez, D.A. Sell,** B. Hughes, A. Acharya,
ARIZONA STATE UNIVERSITY,
Department of Physics, of Chemistry & Bio-Chemistry Tempe, AZ 85287-1504,
* SiO2 NanoTech LLC,Tempe, AZ 85282
** Marquette University, Marquette, WI
*** Caltech, Pasadena, CA

R.L. Rhoades, Scott N.  Drews 
Entrepix, Inc. Tempe AZ 85282.

Hydroxylated silica about 2.1 ± 0.1 nm thick are nucleated on OH(1x1)Si(100) as precursor phase to cross-bond directly silica to Si, and silica to silica using planarization via extended atomic terraces,  T≤ 200°C, an H2O/O2 ambient, and p ≥ 1 atm. This method, "Wet Nano-Bonding™”, relies on the Herbots-Atluri process [1] to nucleate precursor phases to bond via direct hydroxylated silica molecular cross-bridges two surfaces brought into contact at the nano-scale. 
Ordered Si2(OH)4 β-cristobalite precursor phases exhibit atomic terraces that extend to > 20 nm, in contrast to the 2 nm width in "as received" Si(100) wafers. β-cristobalite nano-phases can desorb at low temperatures (T </~ 200 °C) [3]. These ordered oxides can promote the growth of flatter, smoother, better controlled oxides at low temperatures in ambient air. When put into close contact at T≥ 200°C with oxygen-deficient phases of SiOx used in microelectronics, they can consistently nucleate a cross-bridging between the two substrates, or “nano-bonding” inter-phase [4] between various combinations Si and silica provided an H2O/O2 ambient catalyzes low temperature oxidation and nano-contacting is achieved via pressurization in the nano-bonding chamber.

[1] V. Atluri et al MRS Symp. Proc. Vol 477 (1997)
[2] N. Herbots et al. Mater. Sc. & Eng, B87 (2001), 303
[3] N. Herbots et al., US patent 6,613,617 (2003) & 7,851,365 (2011)
[4]  K.T. Queeney et al. Appl. Phys. Lett., Vol. 84, No. 4, 26 (2004)"

To have a better understanding on how ZnTe semiconductor nanoparticles were obtained by high-energy milling under composition, pressure and temperature vial conditions reached during milling, a molar Zn–Te–O ternary representation was disclosed. Through this approach, all the bulk and surface chemical transitions were revealed as: i) stable, ii) stoichiometric and iii) metastable or non-stoichiometric reaction products in the Zn–Te–O molar system. Surface studies (via X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy) and bulk analyses (X-ray diffraction and secondary ion mass spectrometry) were carried out to find out the mechanism of formation of the ZnTe semiconductor nanoparticles. The results showed that the as-milled ZnTe nanoparticles were polycrystalline – with a slight presence of amorphous phases – and chemically homogeneous (according to elemental chemical mapping of Zn K-line and Te L-line). Thus, the way in which the oxygen chemical potential was decreased from Zn2Te3O8 to ZnTe nanoparticles was proposed. Consequently,
predicted transitions in the ternary molar representation were consistent with experimental results. A blue shift of the ZnTe nanoparticles (at 10 h milling time) was observed by optical measurements. It implied an  enhancement in its direct band gap, attributed to the presence of nanoparticles and coarse particles with both, embedded quantum dots and nanoparticles.

The need for tighter control over film uniformity, conformality, and properties at decreasing thicknesses was met by a gradual evolution from physical vapor deposition (PVD), to chemical vapor deposition (CVD), and eventually atomic layer deposition (ALD) processes.  Of all manufacturing-worthy thin-film deposition processes, ALD has the greatest potential to satisfy these requirements.  However, the intrinsic constraints of recurrent two atom reactivity and associated byproducts have kindled tremendous interest in other self-limiting deposition processes such as Molecular Layer Deposition (MLD), Self-Assembled Monolayer (SAM), and “Click” Chemistry Deposition (CCD)  processes, either as alternatives to or in conjunction with ALD.  This overview provides definitions, illustrations and examples of these processes.

This paper describes an analytical model developed to study the Fano resonance effect in clusters of spherical plasmonic nanoparticles under local excitation. The model depicted the case of a parallel single dipole emitter that was near-field coupled to a pentamer or heptamer cluster of nanospheres. Spatial polarization and field distributions of the optical states and resonance spectra for these cluster configurations were calculated. It was discovered that polarization interference between the nanoparticles triggered the formation of a second peak in the directivity spectra at 690 nm, and this in turn provided a mechanism for the occurrence of subradiant mode effects. The directivity calculation was analyzed in order to qualify the redirection of emission. Performances of various nanoantennae were investigated and fully characterized in terms of spatial geometric differences and the Fano resonance effect on plasmonic nanoparticles in the optical domain. Light radiation patterns were found to be significantly affected by nanosphere sizes and positioning of nanospheres with respect to the dipole. The analytical treatment of these modeled nanoantennae yielded results that are applicable to physical design and utilization considerations for pentamer and heptamer clusters in nanoantennae mechanisms.

http://link.springer.com/article/10.1007/s00339-014-8832-2

Quantum dots (QDs) are steadily being implemented as down-conversion phosphors in market-ready display products to enhance color rendering, brightness , and energy efficiency. However, for adequate longevity, QDs must be encased in a protective barrier that separates them from ambient oxygen and humidity, and device architectures are designed to avoid significant heating of the QDs as well as direct contact between the QDs and the excitation source. In order to increase the utility of QDs in display technologies and to extend their usefulness to more demanding applications as, for example, alternative phosphors for solid-state lighting (SSL), QDs must retain their photoluminescence emission properties over extended periods of time under conditions of high temperature and high light flux. Doing so would simplify the fabrication costs for QD display technologies and enable QDs to be used as down-conversion materials in light-emitting diodes for SSL, where direct-on-chip configurations expose the emitters to temperatures approaching 100 °C and to photon fluxes from 0.1 W/mm 2 to potentially 10 W/mm 2. Here, we investigate the photobleaching processes of single QDs exposed to controlled temperature and photon flux. In particular, we investigate two types of room-temperature-stable core/thick-shell QDs, known as " giant " QDs for which shell growth is conducted using either a standard layer-by-layer technique or by a continuous injection method. We determine the mechanistic pathways responsible for thermally-assisted photodegradation, distinguishing effects of hot-carrier trapping and QD charging. The findings presented here will assist in the further development of advanced QD heterostructures for maximum device lifetime stability.

In order to interpret the electrical characteristics of fabricated Au/ZnO/n-Si structures as a function of frequency and voltage well, their capacitance– voltage (C–V) and conductance–voltage (G/x–V) measurements were carried out in a wide range of frequencies (0.7 kHz–2 MHz) and voltages (± 6 V) by 50 mV steps at room temperature. Both the C–V and G/x–V plots have reverse, depletion, and accumulation regions such as a metal–insulator/oxide semiconductor (MIS or MOS) structures. The values of doped-donor atoms (N D), Fermi energy level (E F), barrier height (U B), and series resistance (R s) of the structure were obtained as a function of frequency and voltage. While the value of N D decreases with increasing frequency almost as exponentially, the value of depletion width (W D) increases. The values of C and G/x increase with decreasing frequency because the surface states (N ss) are able to follow the alternating current (AC) signal, resulting in excess capacitance (C ex) and conductance (G ex /x), which depends on their relaxation time and the frequency of the AC signal. The voltage-dependent profiles of N ss were obtained from both the high–low frequency capacitance and Hill-Colleman methods. The other important parameter R s of the structure was also obtained from the Nicollian and Brews methods as a function of voltage.

Au/graphene oxide (GO)-doped PrBaCoO nanoceramic/n-Si capacitors were fabricated and their admittance measurements were carried out between 1 kHz and 1 MHz at room temperature. Experimental results showed that the capacitance (C) and conductance (G/w) values are strong functions of frequency and applied bias voltage. C–V plot revealed two distinctive peaks at low frequencies which are located at about 0 and 2 V, such that the first peak disappears towards high frequencies. The energy density distribution profile of the interface/surface states (D it / N ss) and their relaxation time (s) and capture cross section (r p) of the sample were obtained by using the admittance method. In addition, the voltage-dependent profile of N ss and resistance were obtained by using low–high frequency capacitance and Nicollian-Brews method, respectively, and they also reveal two distinctive peaks, respectively. Two peaks' behavior in the forward bias C–V, N ss –V and R i –V plots confirmed the existence of two different localized regions of N ss between Si and interfacial layer. The series resistance (R s) of the device decreased with increasing frequency from 175 X at 1 kHz to 72 X at 1 MHz. As a result, the mean value of D it was found about 5 9 10 13 eV-1 cm-2 which is reasonable for an electronic device.

Presented here is a patent in the Bulgarian register of inventions (Reg. № 41177/1978), written in Bulgarian. The patent relates to uniform deposition of semiconducting and insulating thin films in cold gas plasma. Various flat substrates can be used, semiconductor ones in particular. The claims relate to a specific configuration of the reactor chamber by which uniformity of the (static part of) gas plasma is achieved. That feature results in improved uniformity of the thus deposited thin films, as compared to the one achieved by the existing systems. The application of this method is demonstrated on Si3N4 and SiO2 thin layers deposited onto Silicon wafers, aimed for the mass production of MOS IC’s (Metal-Oxide-Semiconductor Integrated Circuits).

The invention described features one claim. The description is supported by two drawings.

Optical metrology techniques are essential for process control of gate formation process steps from lithography to the dielectric, spacers, gate and straining layer deposition in sub-90nm technology nodes. Traditionally, optical metrology is based on the measurement of periodic lines or hole arrays using a spectroscopic ellipsometer or reflectometer, collecting data across a wide wavelength spectrum at a single angle of incidence. In this paper, we present results of measurements on periodic Poly-Si gate line arrays using laser based Focused Beam Scatterometry (FBS), illuminating at 3 discrete laser wavelengths while data is collected over an angle of incidence range from 45° to 65°. Accuracy, repeatability, and tool-to-tool matching results for the poly-Si gate line arrays are discussed. Comparison with the CD-SEM and cross-section TEM result for measurement/modeling accuracy is also presented.

Strong electrophilic natured acetaldehyde present in various food and beverages damages genetic material and induces diseases like atherosclerosis. Detection and quanti fi cation of such a carcinogen poses a major challenge. In this context, a novel room temperature acetaldehyde sensor made up of hierarchical ZnO nanostructures and prepared by a simple and template-free method has been reported. ZnO nanostructures were grown on glass substrates by a chemical spray pyrolysis technique at the substrate temperature of 523 K. Di ff erent nanostructures, namely tiny nanoplatelets, branched nanorods and thicker nanoplatelets, were formed by an annealing process. The crystal structures, morphologies and optical absorbances of the hierarchical ZnO nanostructures were investigated by X-ray di ff raction (XRD), field emission scanning electron microscopy (FE-SEM) and UV-vis spectrophotometry, respectively. The branched nanorods showed an excellent sensing response towards 20 to 500 ppm of acetaldehyde
vapour. The role of high density junctions of the branched ZnO architecture in enhancing the vapour sensing performance has been highlighted. The observed selectivity, range of detection and stability of the branched ZnO nanorods have proven their potential as a sensing element for the detection of acetaldehyde.

"This invention relates to methods for bonding substrates, and in particular, bonding of semiconductor and/or semiconductor oxide and nitride wafers.

Abstract: Substrates may be bonded according to a method comprising contacting a first bonding surface of a first substrate with a second bonding surface of a second substrate to form an assembly; and compressing the assembly in the presence of an oxidizing atmosphere under suitable conditions to form a bonding layer between the first and second surfaces, wherein the first bonding surface comprises a polarized surface layer; the second bonding surface comprises a hydrophilic surface layer; the first and second bonding surfaces are different. ...

BACKGROUND

The long-term reliability of multicomponent devices such as bio-sensors and solar cells is at least in part determined by the robustness of the bonding methods used to hold the devices together. Typically, epoxy bonding methods are used to prepare such devices, but suffer from the limitations of limited longevity (10 years) as well as poor thermal matching between components which can lead to internal stresses and ultimately bonding failure. Implantable bio-sensor devices need to be hermetically sealed in a saline environment such as a human or an animal body for the lifetime of the implant.

As many biosensors and solar cells are typically based on silica wafers (borosilicate, alpha-quartz, etc.) and Si(100) wafers, there exists a need in the art for improved methods for bonding the same together. In particular, there exists a need for methods which can provide hermetically sealed devices which may be implanted into the human body. Additionally, there exist needs to improve the temperature and pressure requirements of bonding for such applications. There is also a need to improve the bonding between a broader range of materials for such applications.

SUMMARY

OF THE INVENTION
Accordingly, in a first aspect, the invention provides methods for bonding substrates comprising contacting a first surface of a first substrate with a second surface of a second substrate to form an assembly; and compressing the assembly in the presence of an oxidizing atmosphere under suitable conditions to form a bonding layer between the first and second surfaces, wherein the first surface comprises a polarized surface layer; the second surface comprises a hydrophilic surface layer; the first and second surfaces are different.

In another aspect, the invention provides methods for bonding substrates comprising contacting a first bonding surface comprising O2H2Si(1×1)(100) of a first substrate comprising Si with a second bonding surface of a second substrate comprising a silicate to form an assembly; and compressing the assembly in the presence of an oxidizing atmosphere under suitable conditions to form a bonding layer between the first and second bonding surfaces.

In another aspect, the invention provides methods for bonding substrates comprising contacting a first bonding surface comprising hydroxy-terminated silica of a first substrate comprising a silicate with a second bonding surface comprising SiOx, where 0<x≦2, of a second substrate comprising a silicate to form an assembly; and compressing the assembly in the presence of an oxidizing atmosphere under suitable conditions to form a bonding layer between the first and second bonding surfaces.

In a second aspect, the invention provides the bonded substrates formed according to the first aspect of the invention.

In a third aspect, the invention provides implantable medical devices comprising a bonded substrate of the second aspect of the invention.

In a fourth aspect, the invention provides solar cells comprising a bonded substrate of the second aspect of the invention."

We report the results of direct measurements and a theoretical investigation of the in-plane effective mass in the two-dimensional electron gas of nominally undoped AlGaN/GaN heterostructures with a different degree of quantum confinement. It is shown that in most cases the conduction band nonparabolicity effect is overestimated and the electron wave-function penetration into the barrier layer should be taken into account. The contribution of the wave-function hybridization is determined to play the dominant role. The band edge effective mass value is deduced to be (0.2+-0.01) m0.