Nanostructured ZnTe films prepared by D.C. magnetron sputtering
TL;DR: The shift of the band gap to higher energies depended on the relative magnitudes of substrate temperature and gas pressure during deposition as mentioned in this paper, and the relative magnitude of temperature and pressure during the sputtering of a ZnTe target was determined.
Abstract: ZnTe films in nanostructured form have been deposited by high pressure d.c. magnetron sputtering of a ZnTe target onto different substrates kept at various temperatures ranging from 223–373 K. Shift of the band gap to higher energies depended on the relative magnitudes of substrate temperature and gas pressure during deposition.
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TL;DR: In this article, Efros and Shklovskii hopping within the Coulomb gap was found to be the predominant carrier transport process in the lower temperature region in these nanocrystalline GaN films.
Abstract: Nanocrystalline GaN films were deposited on quartz substrates at ∼25 Pa with deposition temperature within 210–270 K using high pressure magnetron sputtering technique. Electrical, galvanomagnetic and microstructural properties were measured at different temperatures for these films. Studies on the variation of conductivity with temperature indicated Efros and Shklovskii (E–S) hopping within the Coulomb gap to be the predominant carrier transport process in the lower temperature region in these nanocrystalline GaN films. A cross-over from Mott's hopping in higher temperature region to E–S hopping in the “soft” Coulomb gap was noticed with lowering of temperature. Hall mobility was found to be dominated by the combined effects of scattering from ionized impurities, acoustic phonon and non-polar optical phonons.
9 citations
TL;DR: In this article, an indium phosphide film was deposited by flash evaporating InP powder (99.995%) on glass substrates and X-ray diffraction traces indicated reflections from (111, (220) and (311) planes only.
Abstract: Indium phosphide films were deposited by flash evaporating InP powder (99.995%) on glass substrates. Microstructural information was obtained from transmission electron microscope and atomic force microscope (AFM) studies. The average value (~ 0.33 nm) of surface roughness of the films was determined by AFM. X-ray diffraction traces indicated reflections from (111), (220) and (311) planes only. The band gap was found to vary between ~ 1.94 eV and 1.96 eV. e∞ varied between 11.58 and 11.89 while the plasma frequency (ωp,) were seen to vary between 8.52 and 8.59 × 1014 s− 1. The bonding environment in the films was determined from Raman and Fourier transformed infrared measurements. The experimental absorption spectra could be faithfully described by considering the effect of scattering by the ultra small crystallites in the film alone. Photoluminescence peak located at ~ 1.5 eV may be ascribed due to transitions from states arising out of phosphorous vacancy to the valance band. The shoulders of the peak ~ 1.5 eV may originate from the DA transitions between VP and InP.
9 citations
TL;DR: In this paper, the electrical properties of CdTe and optical properties of ZnS in nanocrystalline thin film form were studied with a view to have a clearer understanding of the optical processes and the carrier transport mechanisms in naniscale II-VI semiconductors, in general.
Abstract: The electrical properties of CdTe and optical properties of ZnS in nanocrystalline thin film form are studied with a view to have a clearer understanding of the optical processes and the carrier transport mechanisms in nanocrystalline II–VI semiconductors, in general. Nanocrystalline ZnS and CdTe films were deposited by magnetron sputtering of respective targets in argon plasma. The optical absorption data of nanocrystalline ZnS films (thickness 10–40 nm) could be explained by the combined effects of phonon and inhomogeneity broadening along with optical loss due to light scattering at the nanocrystallites. The conductivity of CdTe (grain size within 4–4·7 nm) showed (T
0/T)
p
dependence withp ∼ 0·5 indicating the presence of a Coulomb gap near the Fermi level. The width of the Coulomb gap varied within 0·02–0·04 eV depending on the deposition condition. The existing theoretical models were used for estimating hopping energy (0·02–0·04 eV) and hopping distance (2·8–5·1 nm) in nano CdTe films.
9 citations
TL;DR: SiO2/n-GaN/SiO 2 composite films in the nanocrystalline form were deposited using a multi-target sputtering system onto fused silica substrates at a system pressure ~25 Pa as mentioned in this paper.
Abstract: SiO2/n-GaN/SiO2 composite films in the nanocrystalline form were deposited using a multi-target sputtering system onto fused silica substrates at a system pressure ~25 Pa. Different sets of nanocomposite films with different ratios of the sizes of the nanocrystallites (d) and intercrystallite distances (s) were deposited by changing the substrate temperature during sequential sputtering of the targets. The films were characterized by measuring the microstructural and optical properties. Photoluminescence measurements were carried out at 300 K. The experimental absorption spectra could be faithfully described by considering the combined effect of scattering by the ultra-small crystallites and broadening due to inhomogeneity in the sizes of the films.
8 citations
TL;DR: In this paper, ZnS thin films were deposited by rf-magnetron sputtering using, nanocrystalline powder synthesized by solvothermal/hydrothermal route.
Abstract: Zinc Sulfide (ZnS) has been proposed as a novel buffer layer, alternative to CdS for solar cell applications. ZnS thin films were deposited by rf-magnetron sputtering using, nanocrystalline powder synthesized by solvothermal/hydrothermal route. ZnS nanoparticles with a grain size between 10 and 20 nm were obtained by simple solvothermal/hydrothermal technique. The powders as synthesized were used to develop the buffer layers of nanostructured ZnS by rf-magnetron sputtering. The structural, surface morphology and optical properties of the films were studied. The as-deposited ZnS films were polycrystalline textured and a very smooth surface was obtained. The films are highly transparent in the visible wavelength region with a transmittance higher than 85 %.
8 citations
References
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Book•
[...]
01 Jan 1959
TL;DR: In this paper, the authors discuss various topics about optics, such as geometrical theories, image forming instruments, and optics of metals and crystals, including interference, interferometers, and diffraction.
Abstract: The book is comprised of 15 chapters that discuss various topics about optics, such as geometrical theories, image forming instruments, and optics of metals and crystals. The text covers the elements of the theories of interference, interferometers, and diffraction. The book tackles several behaviors of light, including its diffraction when exposed to ultrasonic waves.
19,815 citations
[...]
01 Oct 1999
TL;DR: In this article, the authors discuss various topics about optics, such as geometrical theories, image forming instruments, and optics of metals and crystals, including interference, interferometers, and diffraction.
Abstract: The book is comprised of 15 chapters that discuss various topics about optics, such as geometrical theories, image forming instruments, and optics of metals and crystals. The text covers the elements of the theories of interference, interferometers, and diffraction. The book tackles several behaviors of light, including its diffraction when exposed to ultrasonic waves.
19,503 citations
2,822 citations
TL;DR: In this article, an extensive numerical calculation for the eigenvalue problem is carried out by Ritz's variational technique, and the motional state of the lowest level is classified into three regimes: the regime of exciton confinement for R/${a}_{B}^{\mathrm{*}}$\ensuremath{\gtrsim}4, the regime for individual particle confinement forR/${b}^{*}+1.2.
Abstract: Quantum-size effects of an electron-hole system confined in microcrystals of semiconductors are studied theoretically with the spherical-dielectric continuum model. An extensive numerical calculation for the eigenvalue problem is carried out by Ritz's variational technique. The motional state of the lowest level is classified into three regimes: the regime of exciton confinement for R/${a}_{B}^{\mathrm{*}}$\ensuremath{\gtrsim}4, the regime of individual particle confinement for R/${a}_{B}^{\mathrm{*}}$\ensuremath{\lesssim}2, and the intermediate regime for 2\ensuremath{\lesssim}R/${a}_{B}^{\mathrm{*}}$\ensuremath{\lesssim}4, where R is the radius of the quantum well and ${a}_{B}^{\mathrm{*}}$ is the exciton Bohr radius. In the region R/${a}_{B}^{\mathrm{*}}$\ensuremath{\gtrsim}4, the high-energy shift of the lowest exciton state is described by the rigid-sphere model of the exciton quite well, which takes into account the spatial extension of the relative motion of the electron and the hole. The oscillator strength of the interband optical transition changes dramatically across the region 2\ensuremath{\lesssim}R/${a}_{B}^{\mathrm{*}}$\ensuremath{\lesssim}4. The metamorphosis of the absorption spectrum is shown as a function of R/${a}_{B}^{\mathrm{*}}$ and compared with the experimental data.
1,119 citations
AT&T1
TL;DR: In this paper, a review and analysis of the optical properties of quantum crystallites, with principal emphasis on the electro-optic Stark effect and all optical third order nonlinearity is presented.
Abstract: This is a review and analysis of the optical properties of quantum crystallites, with principal emphasis on the electro-optic Stark effect and all optical third order nonlinearity. There are also introductory discussions on physical size regimes, crystallite synthesis, quantum confinement theory, and linear optical properties. The experiments describe CdSe crystallites, exhibiting strong confinement of electrons and holes, and CuCl crystallites, exhibiting weak confinement of the exciton center of mass. In the CdSe system, neither the Stark effect nor the third order nonlinearity is well understood. The Stark shifts appear to be smaller than calculated, and field inducted broadening also occurs. The third order nonlinearity is only modestly stronger than in bulk material, despite theoretical prediction. Unexpectedly large homogeneous widths, due to surface carrier trapping, in the nominally discrete crystallite excited states appear to be involved. The CuCl system shows far narrower spectroscopic homogeneous widths, and corresponds more closely to an ideal quantum dot in the weak confinement limit. CuCl also exhibits exciton superradiance at low temperature. Surface chemistry and crystallite encapsulation are critical in achieving the predicted large Stark and third order optical effects in II-VI and III-V crystallites.
995 citations