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 paper, electrical conductivities of nanocrystalline CdTe films deposited onto quartz substrates by high-pressure (~20 Pa) DC magnetron sputtering were studied as a function of temperature.
Abstract: Electrical conductivities of nanocrystalline CdTe films deposited onto quartz substrates by high-pressure (~20 Pa) DC magnetron sputtering were studied as a function of temperature (188–298 K). The grain size varied within 4 to 4.7 nm with the variation of deposition temperature (Ts) within 253 to 273 K. The conductivity (σ) showed (T0/T)p dependence with p~0.5 indicating the presence of a Coulomb gap near the Fermi level. Efros–Shklovskii (ES) hopping was found to be the predominant carrier conduction mechanism in the nanocrystalline CdTe films. The width of the Coulomb gap varied within 27–41 meV depending on the deposition conditions. Cross-over from ES to Mott's hopping was observed. The existing theoretical models were used for estimating hopping energy (29 to 42 meV) and hopping distance (2.8 to 5.1 nm) in the films.
21 citations
TL;DR: In this paper, the optical transmission, optical absorption, Raman effect and photoluminescence of the nanocrystals have been studied and the observed blueshift of the band gap due to a reduction in the crystallite size is correlated with the transmission electron microscopy observation.
Abstract: Silicon nanocrystals have been prepared in thin-film form by a dc magnetron sputtering technique. The optical transmission, optical absorption, Raman effect and photoluminescence of the nanocrystals have been studied. The observed blueshift of the band gap due to a reduction in the crystallite size is correlated with the transmission electron microscopy observation. Raman spectra indicated the presence of a TO mode which showed redshift with the decrease in the size of the nanocrystallites.
18 citations
TL;DR: In this article, nanocrystalline ZnSe films were deposited onto glass, quartz and NaCl substrates by sputtering of a znSe target in argon plasma and optical, microstructural, and photoluminescence studies were carried out in order to understand the quantization effect, along with optical absorption and emission processes, in the material in nanocrystine form.
Abstract: Nanocrystalline ZnSe films were deposited onto glass, quartz and NaCl substrates by sputtering of a ZnSe target in argon plasma. Optical, microstructural, and photoluminescence studies were carried out in order to understand the quantization effect, along with optical absorption and emission processes, in the material in nanocrystalline form. © 1997 Acta Metallurgica Inc.
16 citations
TL;DR: In this paper, Schottky diodes of structure Au/nano-CdS/CBD-CDS/SnO 2 were fabricated with the nanocrystalline CdS layer deposited by the high pressure magnetron sputtering technique.
Abstract: Schottky diodes of structure Au/nano-CdS/CBD-CdS/SnO 2 were fabricated with the nanocrystalline CdS layer deposited by the high pressure magnetron sputtering technique. The devices were characterized by current-voltage (I-V) anti capacitance-voltage (C-V) measurements. It was observed that the presence of a large amount of surface states might explain the high values of n in the nano-devices. The quantization effects of the active nano-CdS layer in the devices was confirmed from the observed peaks in the plot of conductance versus reverse bias voltage.
15 citations
TL;DR: In this paper, the photoluminescence (PL) spectra of GaN nanocrystalline GaN films with different crystallite sizes were deposited onto quartz and NaCl substrates by magnetron sputtering of a GaN target.
Abstract: Nanocrystalline GaN films with different crystallite sizes were deposited onto quartz and NaCl substrates by magnetron sputtering of a GaN target in argon plasma. All the films showed predominant hexagonal phase. The band gap values were always found to be higher than that of the bulk. This blue shift in band gap could be attributed to the quantum confinement effect. The optical absorption in these films could be explained by the combined effects of phonon and inhomogeneity broadening along with optical loss due to light scattering at the nanocrystallites. Band edge luminescence is absent in these GaN nanocrystalline films. The line shapes of the photoluminescence (PL) spectra are asymmetric and broad. The film deposited at lower substrate temperature showed broader PL peak. It may be observed that no significant energy shift in the peak positions was observed with reduction in crystallite size but the intensity of the peak decreased for films with the reduction in crystallite size. Below band gap emission observed in this study may also originate due to the presence of polarization-induced electric field present in wurtzite GaN deposited here.
14 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