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We critically examine how two processing steps commonly applied in the preparation of cadmium telluride (CdTe)-based solar cells, i.e., the cadmium chloride treatment and the subsequent stepwise bromine/methanol wet etching process, impact the structural and optical properties of polycrystalline CdTe thin-films. In particular, drawing upon a conjuncture of photothermal deflection spectroscopy and spectroscopic ellipsometry experimental results, we determine the spectral dependence of the optical absorption coefficient, α(E), over the photon energy range from 1.1 to 2.0 eV for samples of rf sputtered (RFS) and close space sublimation (CSS) CdTe. The impact of these processing steps on shaping the grazing incidence x-ray diffraction pattern is also examined. We extend the analysis to devices through interpretation of the spectral dependence of the external quantum efficiency associated with two cadmium chloride treated CdTe-based solar cells. The cells are comparably prepared with the exception of the absorber, one by RFS and the other by CSS. Through the use of our results for the thin-film CdTe optical functions and a model for the solar cell multilayer structure, we simulate the resultant external quantum efficiency spectrum. Through a critical contrast with the corresponding solar cell acquired experimental results, we glean insights into the carrier trapping and recombination processes that occur within the two types of CdTe absorbers. [ABSTRACT FROM AUTHOR]

A demonstration of the principles of quantum key distribution (QKD) is performed using a single-photon source in a proof of concept test-bed over a distance of 2 km in standard telecommunications optical fiber. The single-photon source was an optically-pumped quantum dot in a microcavity emitting at a wavelength of 895 nm. Characterization of the QKD parameters was performed at a range of different optical excitation powers. An investigation of the effect of varying the optical excitation power of the quantum dot microcavity on the quantum bit error rate and cryptographic key exchange rate of the system are presented. [ABSTRACT FROM AUTHOR]

Long-range surface plasmons traveling on thin metal films have demonstrated promising potential in subwavelength waveguide applications. In work toward device applications that can leverage existing silicon microelectronics technology, it is of interest to explore the propagation of surface plasmons in a metal-oxide-semiconductor geometry. In such a structure, there is a high refractive index contrast between the semiconductor (n≈3.5 for silicon) and the insulating oxide (typically n≈1.5-2.5). However, the introduction of dielectrics with disparate refractive indices is known to strongly affect the guiding properties of surface plasmons. In this paper, we analyze the implications of high index contrast in 1D layered surface plasmon structures. We show that it is possible to introduce a thin dielectric layer with a low refractive index positioned next to the metal without adversely affecting the guiding quality. In fact, such a configuration can dramatically increase the propagation length of the conventional long-range mode. While this study is directed at silicon-compatible waveguides working at telecommunications wavelengths, this configuration has general implications for surface plasmon structure design using other materials and operating at alternative wavelengths. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We have developed a Kramers-Kronig consistent analytical expression to fit the measured optical functions of hydrogenated amorphous silicon (a-Si:H) based alloys, i.e., the real and imaginary parts of the dielectric function (∈[sub 1], ∈[sub 2]) (or the index of refraction n and absorption coefficient α) versus photon energy E for the alloys. The alloys of interest include amorphous silicon-germanium (a-Si[sub 1-χ]Ge[sub χ] :H) and silicon-carbon (a-Si[sub 1-χ]C[sub χ] :H), with band gaps ranging continuously from ∼1.30 to 1.95 eV. The analytical expression incorporates the minimum number of physically meaningful, E independent parameters required to fit (∈1, ∈[sub 2]) versus E. The fit is performed simultaneously throughout the following three regions: (i) the below-band gap (or Urbach tail) region where a increases exponentially with E, (ii) the near-band gap region where transitions are assumed to occur between parabolic bands with constant dipole matrix element, and (iii) the above-band gap region where (∈[sub 1], ∈[sub 2]) can be simulated assuming a single Lorentz oscillator. The expression developed here provides an improved description of ∈[sub 2] (or α) in the below-band gap and near-band gap regions compared with previous approaches. Although the expression is more complicated analytically, it has numerous applications in the analysis and simulation of thin film a-Si:H based p-i-n and n-i-p multilayer photovoltaic devices. First, we describe an approach whereby, from a single accessible measure of the optical band gap, the optical functions can be generated over the full solar spectrum for a sample set consisting of the highest quality intrinsic a-Si:H based alloys prepared by plasma-enhanced chemical vapor deposition using the principle of maximal H[sub 2] dilution. Second, we describe quantitatively how such an approach can be modified for sample sets consisting of lower quality... [ABSTRACT FROM AUTHOR]

The c[sub 0] lattice parameter, band gap, and photoluminescence spectra of n-type 0.9 μm thick In[sub x]Ga[sub 1-x]N films with x=0, 0.045, 0.085, and 0.140 were examined. The c[sub 0] lattice parameter followed Vegard’s law using c[sub 0]=0.5185 nm for GaN and c[sub 0]=0.569 nm for InN. Band gap measurements by photocurrent spectroscopy fit well with data published by one other research group, with the combined set being described by the equation E[sub g]=3.41-7.31x+14.99x[sup 2] for 0≤x≤0.15. Photoluminescence measurements with a pulsed nitrogen laser showed a peak well below the measured band gap, as well as significant luminescence above the measured band gap. The above-gap luminescence appears to be due to band filling by the high intensity laser pulses. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents information on a study which measured the unnormalized Stokes vector by using a rotating-compensator multichannel ellipsometer. Polarization state of light reflected from specular and textured SnO2: F films; Experimental details; Results and discussions.

Presents a study which calculated the atomic depth distribution in solids produced by high-speed ion bombardment using the concept of the effective displacement volume of an atom. General equations used; Constraints on variation of the effective displacement volume with composition; Overview of an extensive survey of binary metal alloys.

Studies the annealing effect on porosity of amorphous hydrogenated carbon films using a quartz crystal microbalance. Background to the study; Experimental procedures; Results and discussion.

Presents a study that investigated the reliability of the diffusion approximation for the ballistic relocation function in atomic mixing by ion beams. Information on mixing equations; Numerical results; Conclusion.

Presents a study which reported the results of ellipsometry measurements performed during the growth of hydrogenated amorphous silicon thin films on crystalline silicon substrates. Formation of low-density microstructure in the initial stages of growth; Effect of sputtering on the glow-discharge decomposition of gases; Discussion on the pseudodielectric function trajectories.

Presents information on a study which extended in situ ellipsometry characterization of the nucleation and microstrucutral evolution of amorphous silicon (a-Si:H) to the effect of deposition parameters on these processes. Details about the structural evolution of a-Si:H; Important aspects of the ellipsometer/glow-discharge reactor system; General features of in situ trajectories.

Presents a study which examined the effect of substrate microstructure on the growth habit of high-quality hydrogenated amorphous silicon. Experimental details; Results and discussion; Conclusion.

Presents information on a study that examined the growth and microstructure of α-Si:H/α-SiN [subx] :H heterojunctions. Experimental details; Results and discussion on the study; Conclusions.

Presents information on a study which analyzed the in situ ellipsometry measurements taken during the deposition of hydrogenated amorphous silicon on crystalline silicon substrates in a convention rf glow-discharge apparatus. Nucleation behavior of hydrogenated amorphous silicon; Experimental details; Results and discussion; Conclusions.

Presents the results of the application of photoresponse techniques to the study of the transport of electrons past an energy barrier. Investigations of electron transport through gallium arsenide/aluminum arsenide heterostructures; Model for the absorption of the light in the structures used; Change in the band gap as compared to the shift in the peak position in the voltage spectrum of the second sample.

Examines the optical properties of ion-beam-sputtered silicon and germanium using spectroscopic ellipsometry. Discrepancies between the structure of the p-silicon deduced from Raman and ellipsometry spectra; Significance of thin-film polycrystalline silicon; Psuedodielectric functions for ion-beam-deposited silicon prepared at different substrate temperatures.

Analyzes the structure of a hydrogenated amorphous silicon based n-1 two-layer system using spectroscopic ellipsometry measurements. Details on the experiment; Data analysis; Results of the study.

Presents a study which examined the optimization and analysis of solar selective surfaces with continuous and multilayer profiles. Theory and computation method; Results and discussion; Conclusions.

Investigates the growth rate and optical properties of thin nanocrystalline diamond films prepared over a range of the carbon monoxide(CO)/H[sub2] ratio, using real time spectroellipsometry (RTSE). Comparison between diamond growth and properties from CO/H[sub2] and CH[sub4]/H[sub2]/O[sub2] at similar phase-diagram points; Advantage of RTSE over Raman spectroscopy for characterizing and optimizing nanocrystalline diamond film; Significance of methyl radical for diamond film growth.

Discusses a study which applied a real time spectroellipsometry data analysis procedure to characterize depth profiles in the optical gap for semiconductor alloy thin films prepared by plasma enhanced chemical vapor deposition. Theoretical background; Description of the experimental setup; Findings.

Presents information on a study which investigated the stress in diamond films prepared by microwave plasma chemical vapor deposition as a function of methane concentration and deposition temperature. Calculation of thermal stress; Dependence of the total and intrinsic stress on methane concentration; Stress dependence on deposition temperature; Origin of tensile intrinsic stress.

Presents a study which examined a general model matching the thin-skin electromagnetic field around surface-breaking cracks in metals. General formulation; Calculation of the magnetic field above the flow; Conclusions.

Describes a numerical iterative scheme which can be used in solving inverse problems encountered in the application of the ac field measurement (acfm) technique for sizing surface breaking cracks in metals. List of methods in detecting metal flaw; Distinguishing feature of acfm; Discussion on the relationship between crack depth and surface potentials.

Studies pressure relaxation in atomic mixing and preferential sputtering. Determination of relocation without relaxation; Measurement of relaxation current; Analysis of the motion of the surface.

Reports on the application of real time spectroscopic ellipsometry to characterize the nucleation of diamond on c-silicon by tungsten filament-assisted chemical vapor deposition (CVD). Stages of diamond growth by filament-assisted CVD; Preparation of the diamond; Information on the structural model and parameters deduced in a linear regression analysis of the final spectra.

Provides information on a study which proposed a field-effect transistor structure based on strain-induced polarization charges. Discussion of the pseudomorphic growth of a barrier layer on a substrate oriented in a polar direction; Observation concerning polarization and piezoelectric effect; Forms at the heterointerface to screen the polarization charges.

Probes the evolution of surface roughness over a wide range of film thickness during the growth of glow discharge hydrogenated amorphous silicon (a-Si:H) using in situ ellipsometry. Differences in the resulting film properties; Factor to which the columnar morphology observed for SiH[sub4]:argon films is attributed; Description of the pseudodielectric function.