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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 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 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.

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.

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.

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.

In situ and ex situ characterization methods have been applied to investigate the properties of (Ag,Cu)InSe2 (ACIS) thin films. Data acquired from real time spectroscopic ellipsometry (RTSE) experiments were analyzed to extract the evolution of the nucleating, bulk, and surface roughness layer thicknesses. The evolution of these layer thicknesses suggests a transition from Volmer-Weber to Stranski-Krastanov type behavior when Cu is replaced by Ag. The complex dielectric functions of ACIS at both deposition and room temperature as a function of film composition were also extracted from the RTSE data, enabling parameterization of the alloy optical properties. [ABSTRACT FROM AUTHOR]

Silver nanoparticle films were deposited by sputtering at room temperature and were annealed while monitoring by real time spectroscopic ellipsometry (SE). The nanoparticle dielectric functions (0.75 eV-6.5 eV) obtained by SE were modeled using Lorentz and generalized oscillators for the nanoparticle plasmon polariton (NPP) and interband transitions, respectively. The nanoparticle melting point could be identified from variations in the oscillator parameters during annealing, and this identification was further confirmed after cooling through significant, irreversible changes in these parameters relative to the as-deposited film. The variation in melting point with physical thickness, and thus average nanoparticle diameter, as measured by SE enables calculation of the surface energy density. [ABSTRACT FROM AUTHOR]

Optical probes based on polarized light spectroscopy, including spectroscopic ellipsometry (SE) and polarimetry, have been applied in research and process development for the three major' thin-film photovoltaics technologies, including thin-film hydrogenated silicon (Si:H), cadmium telluride (CdTe), and copper indium-galliuiim diselenide (Culn1-xGaxSe2). Real-time SE during materials fabrication has provided insights into the nucleation, coalescence, and structural evolution of these thin films. These insights have led, in turn, to guiding principles for PV performance optimization, as well as future directions for real-time process control. The optical properties deduced simultaneously with the layer thicknesses using real-time SE have been applied to characterize the phase composition of materials (amorphous versus crystalline), the mean free path and grain size, and the relative free carrier concentration. As a result, analytical formulae for the optical properties of PV materials have been developed with free parameters that are linked to basic materials properties. This paper shows how the formulae and associated parameter-property relationships can serve as a database for analyzing complete PV stacks, with future prospects for mapping layer thicknesses and basic materials properties in on-line monitoring applications for large-area PV plates and modules. [ABSTRACT FROM AUTHOR]

A multichannel ellipsometer in the dual rotating-compensator configuration has been developed for applications in real time Mueller matrix spectroscopy of anisotropic surfaces and thin films. The sequence of optical elements for this instrument configuration can be denoted PC[sub 1r](5ω)SC[sub 2r](3ω)A, where P, S, and A represent the polarizer, sample, and analyzer. In this sequence, C[sub 1r] and C[sub 2r] represent the first and second compensators, rotating with angular frequencies of 5ω and 3ω, respectively, where ω=π/T[sub C] is the base angular frequency (corresponding to 2 Hz) and T[sub C]=0.25 s is the fundamental optical period. The instrument can provide 170 point spectra over the wavelength range from 235 nm (5.3 eV) to 735 nm (1.7 eV) in all 16 elements of the unnormalized Mueller matrix with minimum acquisition and repetition times of T[sub C]=0.25 s. In this study, instrumentation calibration procedures are demonstrated in the transmission geometry without a sample, including (i) alignment of the two MgF[sub 2] zero-order biplate compensators, (ii) determination of the retardance and phase spectra for the compensators, (iii) determination of the offset angles for the optical elements, and (iv) characterization of the spectral response function of the ellipsometer. Calibration procedure (iv) allows the (1,1) element of the transmission Mueller matrix to be determined; thus the unnormalized Mueller matrix can be obtained. The dual rotating-compensator multichannel ellipsometer is assessed with respect to its performance in transmission without a sample, and is then applied in the transmission geometry to study anisotropy, depolarization, and light scattering effects for a MgF[sub 2] helicoidally sculptured thin film on a glass substrate. Numerous future applications of this instrument are anticipated for real time analysis of complex surfaces and thin films in the reflection geometry as well. [ABSTRACT FROM AUTHOR]

A unique rapid-scanning ellipsometer employing a rotating polarizer optical configuration and a multichannel detector for a 1.5–4.5 eV spectral range, has been developed recently for real time studies of film growth and surfaces. This is a new application of the photodiode array-based optical multichannel detector that entails waveform analysis of the incident irradiance at each photon energy. For accurate ellipsometric spectra {ψ(hν),Δ(hν)}, the raw data in the form of photon counts, integrated over four or more equal sectors of polarizer rotation, must be corrected for systematic errors originating from the detection system. Simple procedures are described to characterize and correct for the most significant errors including detection system nonlinearity, image persistence, and scattered stray light in the spectrograph/detector enclosure. [ABSTRACT FROM AUTHOR]

Develops a multichannel spectroscopic ellipsometer based on the rotation-compensator principle. Application of thin film growth for real time Stoke vector spectroscopy; Advantage of the ellipsometer design over the rotating-polarizer design; Characterization of the time evolution of light scattering.

An expansion of the capabilities of high-speed, multichanneI spectroscopic ellipsometry (SE) is described that involves simultaneous measurement of the reflectance spectrum along with the two spectra in the ellipsometric angles (ψ, Δ). previously, a novel rotating-polarizer spectroscopic ellipsometer has been perfected that employs a photodiode array detector for high-speed acquisition of (ψ, Δ) spectra, designed for real-time studies of thin-film growth. For a polarizer angular rotation frequency of ω[sub 0], the (ψ, Δ) values at a given photon energy are deduced from the 2ω[sub 0] Fourier components of the detector irradiance, normalized by the dc component. A third parameter, the weighted reflectance R[sub A], can be obtained from the dc component and from a calibration based on the known optical properties of the substrate measured prior to film growth, With (ω[sub 0]/2π) = 12.5 Hz, three-parameter data sets, [ψ(hυ), Δ (h υ), R[sub A](h &upsilonl); 1.5 ≤ h υ ≤ 4.5 eV], can be acquired with a time ' resolution as short as 40 ms. Although R[sub A] provides complementary information to (ψ, Δ), it has yet to be exploited in conjunction with real-time SE until this study. A resilient analysis approach, based on mathematical inversion and least-squares fitting of the real-time three-parameter data sets, is designed to yield the film dielectric functions and thicknesses independently at each time during the early stages of thin-film growth. The three-parameter approach has been. applied successfully in studies of amorphous silicon (a-Si:H) thin films PrePared by plasma-enhanced chemical vapor deposition, and aluminum and silver films prepared by physical vapor deposition. For the a-Si:H films, R[sub A](h ν) exhibits deviations as large as ∼3% from that predicted in modeling (ψ, Δ) alone. The deviations result from light scattering by plasma... [ABSTRACT FROM AUTHOR]

Submonolayer sensitivity to thin-film nucleation and growth in real time on the millisecond scale has been achieved with a unique rotating polarizer multichannel ellipsometer. Continuous spectra in the ellipsometry angles {ψ(hv),Δ(hv)} consisting of ∼50 points from hv=1.5 to 4.3 eV have been obtained with acquisition and repetition times as short as 16 and 32 ms, respectively. As an example of the instrument capabilities, we present results for hydrogenated amorphous silicon (a-Si:H) growth on c-Si by plasma-enhanced chemical vapor deposition at a rate of 400 Å/min. In this example, the acquisition and repetition times are both 64 ms, and at this speed a precision in (ψ,Δ) of ∼0.02–0.03° is obtained under optimum conditions. We observe a-Si:H nucleation in the first 2 s of deposition, and detect relaxation of nucleation-induced surface roughness with submonolayer sensitivity. [ABSTRACT FROM AUTHOR]

In situ spectroscopic ellipsometry was applied to measure the dielectric functions &eh; of polycrystalline CdTe thin films prepared by magnetron sputtering. The observable critical point (CP) energies determined for the films in best fits to d2&eh;/dE2 are shifted relative to those for single crystal CdTe. The energy shift of the critical point designated as En is attributed to in-plane stress X with linear stress coefficient CX(En). By analyzing these shifts, it was found that stress (1) builds with thickness in as-deposited films, (2) relaxes with increasing substrate temperature at fixed thickness, and (3) is relaxed uniformly in CdCl2 treated films. [ABSTRACT FROM AUTHOR]

The dielectric function of Ag nanoparticle films, deduced from an analysis of in situ real-time spectroscopic ellipsometry (RTSE) measurements, is found to evolve with time during deposition in close consistency with the film structure, deduced in the same RTSE analysis. In the nucleation regime, the intraband dielectric function component is absent and plasmon polariton behavior dominates. Only at nuclei contact, does the intraband amplitude appear, increasing above zero. Both intraband and plasmon amplitudes coexist during surface smoothening associated with coalescence. The intraband relaxation time increases rapidly after surface smoothening is complete, also in consistency with the thin film structural evolution. [ABSTRACT FROM AUTHOR]

The dielectric functions [variant_greek_epsilon] of polycrystalline CdS and CdTe thin films sputter deposited onto Si wafers were measured from 0.75 to 6.5 eV by in situ spectroscopic ellipsometry. Differences in [variant_greek_epsilon] due to processing variations are well understood using an excited carrier scattering model. For each sample, a carrier mean free path λ is defined that is found to be inversely proportional to the broadening of each of the band structure critical points (CPs) deduced from [variant_greek_epsilon]. The rate at which broadening occurs with λ-1 is different for each CP, enabling a carrier group speed υg to be identified for the CP. With the database for υg, [variant_greek_epsilon] can be analyzed to evaluate the quality of materials used in CdS/CdTe photovoltaic heterojunctions. [ABSTRACT FROM AUTHOR]

Real-time spectroscopic ellipsometry (RTSE) is shown to be an effective contactless probe of radio frequency magnetron sputtered molybdenum thin films used as the back electrode in chalcopyrite [Cu(In,Ga)Se2] solar cells. A series of Mo thin films was sputtered onto soda-lime glass substrates at Ar pressures ranging from 4 to 20 mTorr. RTSE measurements reveal how Ar pressure affects the nucleation and growth mechanisms that influence the films’ ultimate grain structure and properties. Determinations of the free electron relaxation times at optical frequencies reveal that higher pressures lead to a smaller average grain size and increased void volume fraction. [ABSTRACT FROM AUTHOR]

BiFeO3 thin films have been deposited on (001) SrTiO3 substrates by adsorption-controlled reactive molecular-beam epitaxy. For a given bismuth overpressure and oxygen activity, single-phase BiFeO3 films can be grown over a range of deposition temperatures in accordance with thermodynamic calculations. Four-circle x-ray diffraction reveals phase-pure, epitaxial films with ω rocking curve full width at half maximum values as narrow as 29 arc sec (0.008°). Multiple-angle spectroscopic ellipsometry reveals a direct optical band gap at 2.74 eV for stoichiometric as well as 5% bismuth-deficient single-phase BiFeO3 films. [ABSTRACT FROM AUTHOR]

Real-time spectroscopic ellipsometry with an ultraviolet-extended spectral range (1.5-6.5 eV) has been applied to investigate the sputter deposition of boron nitride (BN) thin films with high cubic content in terms of a two-layer optical model. In this model, the inner and outer layers represent sp[sup 2]- and sp[sup 3]-bonded BN (hBN and cBN), respectively. The thickness evolution of the two layers as well as their dielectric functions over the extended spectral range have been determined. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Hydrogenated amorphous carbon film growth in diamond-like and polymer-like forms has been studied by in situ ellipsometry. The experiments provide accurate values of the optical functions, thickness, and deposition rate in real time. Reactions between the substrate and the gas phase species or film in the initial stages of growth, inaccessible to ex situ probes, have been detected with monolayer resolution. Monolayer changes in near-surface bonding have also been detected. [ABSTRACT FROM AUTHOR]

In situ ellipsometry experiments have been used to probe the structural changes that occur in the initial stages of the growth of microcrystalline silicon ( μc-Si) on single-crystal Si substrates. The initial nucleation of μc-Si appears to occur at well-dispersed sites and ∼100 Å of material with significantly different optical properties than the bulk is buried at the film/substrate interface. The different optical structure of this interface layer is attributed to voids which are trapped when crystalline nuclei merge. These results are contrasted with recent data for hydrogenated amorphous silicon which show that nuclei converge after about 50 Å, leaving material with bulklike optical properties at the substrate interface. [ABSTRACT FROM AUTHOR]

A rotating polarizer multichannel ellipsometer has been optimized for operation well into the ultraviolet (UV) spectral range. With this instrument, 132 spectral points in the ellipsometric parameters (ψ, Δ) over the photon energy range from 1.5 eV (827 nm) to 6.5 eV (191 nm) can be collected in a minimum acquisition time of 24.5 ms, corresponding to one optical cycle of the rotating polarizer. Averages over two and 80 optical cycles (obtained in 49 ms and 1.96 s, respectively) give standard deviations in (ψ, Δ) of less than (0.04°, 0.08°) and (0.007°, 0.015°), respectively, for the energy range from 3.5 to 6.0 eV, as determined from successive measurements of a stable thermally oxidized silicon wafer. Key modifications to previous instrument designs include: (i) a tandem in-line Xe/D[sub 2] source configuration for usable spectral output from 1.5 to 6.5 eV; (ii) MgF[sub 2] Rochon polarizers for high transmission in the UV without the need for optical activity corrections; (iii) a spectrograph with a grating blazed at 250 nm and two stages of internally mounted order-sorting filters; and (iv) nonuniform grouping of the pixels of the photodiode array detector for a more uniform spectral resolution versus photon energy, with energy spreads per pixel group ranging from 0.02 eV at 1.6 eV to 0.05 eV at 5.1 eV. As an example of the application of this instrument, results of real time spectroscopic ellipsometry studies are reported for the deposition of an amorphous silicon nitride thin film by radio-frequency magnetron sputtering onto a silicon wafer substrate. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A multichannel spectroscopic ellipsometer based on the rotating-compensator principle has been applied to obtain the evolution of spectra (1.5–4.0 eV) in the normalized Stokes vector of the light beam reflected from the surface of a nanocrystalline diamond film during growth. Spectra in the ellipsometry angles (ψ, Δ) provide the time evolution of the microstructure and optical properties of the film in thin layers, whereas the spectra in the degree of polarization provide the time evolution of nonuniformities in the growth process attributed to light scattering by diamond nuclei in the initial stage of growth and to thickness gradients over the probed area in thicker layers. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]