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Journal ArticleDOI

Nanocrystalline CdTe films deposited by high-pressure sputtering: carrier transport at low temperature

15 Dec 1999-Thin Solid Films (Elsevier)-Vol. 357, Iss: 2, pp 102-110
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.
About: This article is published in Thin Solid Films.The article was published on 1999-12-15. It has received 21 citations till now. The article focuses on the topics: Nanocrystalline material & Sputter deposition.
Citations
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Journal ArticleDOI
TL;DR: In this article, high pressure (~40 Pa) d.c. sputtering technique in an argon plasma on fused silica substrate was used to prepare nanocomposite films containing silver particles embedded in SiO2 matrix.
Abstract: Nanocomposite films containing silver particles embedded in SiO2 matrix were prepared by high pressure (~40 Pa) d.c. sputtering technique in an argon plasma on fused silica substrate. Particle size and metal volume fraction were tailored by varying the substrate temperature (Ts~233-300 K) and deposition time (15-240 s). Reduction in size and volume fraction of metal particles culminated in blue-shift of the surface plasmon resonance peak in the optical absorbance spectra of the films. Absence of surface plasmon peak in the absorption spectra below a critical particle size and metal concentration of the nanocomposite films and appearance of sharp absorption edge in the absorbance spectra within the UV-VIS range indicated the semiconducting behaviour of the ultrafine silver particles. Experimental absorbance spectra were theoretically simulated by Mie scattering theory and Maxwell-Garnett effective medium theory.

76 citations

Journal ArticleDOI
TL;DR: In this article, a cubic zinc blende structure of CdS:Mn as primary phase and cubic structured α-MnS as secondary phase was revealed by X-ray diffraction.

63 citations

Journal ArticleDOI
TL;DR: In this article, the authors used the shape distribution introduced in the Maxwell?Garnett or Bruggeman effective medium theory to give a reasonable description of the experimentally observed optical absorption spectra.
Abstract: Silver?silica nanocomposite thin films were prepared by high pressure d.c.?sputtering technique. Films deposited at lower substrate temperature showed a narrow distribution of nanoparticles with nearly spherical shape. Increase in substrate temperature resulted in films with a non-uniform size and shape due to the agglomeration of the nanoparticles. This size and shape distribution has a profound effect on the optical absorbance spectra and results in a broad and asymmetric surface plasmon band. A?shape distribution introduced in the Maxwell?Garnett or Bruggeman effective medium theory was found to give a reasonable description of the experimentally observed optical absorption spectra.

53 citations

Journal ArticleDOI
08 Oct 2011-Vacuum
TL;DR: In this paper, the structure and surface morphology of nano-crystalline CdZnTe films were determined by XRD and SEM, which exhibited a typical particle size of 15nm and a blue shift in the absorption with an effective band gap of 2.26

40 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of substrate temperature and post-deposition heat treatment steps on the morphology, structural, optical and electrical properties of thin film CdTe layers grown by vacuum evaporation were investigated.

37 citations

References
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Journal ArticleDOI
Leo Esaki1, Raphael Tsu1
TL;DR: The study of superlattices and observations of quantum mechanical effects on a new physical scale may provide a valuable area of investigation in the fieId of semiconductors.
Abstract: We consider a one-dimensional periodic potential, or "superlattice," in monocrystalline semiconductors formbeyd a periodic variation of alloy composition or of impurity density introduced during epitaxial growth. If the period of a superlattice, of the order of 100A, is shorter than the electron mean free path, a series of narrow allowed and forbidden bands is expected duet o the subdivision of the Brillouin zone into a series of minizones. If the scattering time of electrons meets a threshold condition, the combined effect of the narrow energy band and the narrow wave-vector zone makes it possible for electrons to be excited with moderate electric fields to an energy and momentum beyond an inflection point in the E-k relation; this results ina negative differential conductance in the direction of the superlattice. The study of superlattices and observations of quantum mechanical effects on a new physical scale may provide a valuable area of investigation in the fieId of semiconductors.

2,569 citations

Journal ArticleDOI
TL;DR: In this article, a discussion of conduction in glasses containing transition metal ions is presented, and the Miller-Abrahams term and polaron hopping term tend to zero, giving a decreasing slope of the ln p versus 1/T curve.
Abstract: In a discussion of conduction in glasses containing transition metal ions, the following points are stressed: 1. (a) The process is similar to “impurity conduction” in doped and compensated semi-conductors. 2. (b) There should be two terms in the activation energy, the Miller-Abrahams term and a polaron hopping term. 3. (c) Both terms should tend to zero, giving a decreasing slope of the ln p versus 1/T curve, as T → 0. 4. (d) The Heikes-Ure formula for the thermopower is discussed and a tentative explanation given of the difference between vanadium- and iron-containing glasses.

2,211 citations

01 Jan 1984
TL;DR: In the last fifteen years, there has been a noticeable shift towards impure semiconductors -a shift which came about because it is precisely the impurities that are essential to a number of major semiconductor devices.
Abstract: First-generation semiconductors could not be properly termed "doped- they were simply very impure. Uncontrolled impurities hindered the discovery of physical laws, baffling researchers and evoking pessimism and derision in advocates of the burgeoning "pure" physical disciplines. The eventual banish ment of the "dirt" heralded a new era in semiconductor physics, an era that had "purity" as its motto. It was this era that yielded the successes of the 1950s and brought about a new technology of "semiconductor electronics." Experiments with pure crystals provided a powerful stimulus to the develop ment of semiconductor theory. New methods and theories were developed and tested: the effective-mass method for complex bands, the theory of impurity states, and the theory of kinetic phenomena. These developments constitute what is now known as semiconductor phys ics. In the last fifteen years, however, there has been a noticeable shift towards impure semiconductors - a shift which came about because it is precisely the impurities that are essential to a number of major semiconductor devices. Technology needs impure semiconductors, which unlike the first-generation items, are termed "doped" rather than "impure" to indicate that the impurity levels can now be controlled to a certain extent."

1,904 citations

Journal ArticleDOI
TL;DR: In this paper, the Coulomb interaction between localized electrons is shown to create a soft gap in the density of states near the Fermi level, and the form of the density within the gap is discussed.
Abstract: The Coulomb interaction between localized electrons is shown to create a 'soft' gap in the density of states near the Fermi level. The new temperature dependence of the hopping DC conductivity is the most important manifestation of the gap. The form of the density of states within the gap is discussed.

1,763 citations

Journal ArticleDOI
TL;DR: In this paper, the authors considered a model in which charge is transported via phonon-induced tunneling of electrons between localized states which are randomly distributed in energy and position, and obtained an electrical conductivity of the form
Abstract: By considering a model in which charge is transported via phonon-induced tunneling of electrons between localized states which are randomly distributed in energy and position, Mott has obtained an electrical conductivity of the form $\ensuremath{\sigma}\ensuremath{\propto}\mathrm{exp}[\ensuremath{-}{(\frac{\ensuremath{\lambda}{\ensuremath{\alpha}}^{3}}{{\ensuremath{\rho}}_{0}\mathrm{kT}})}^{\frac{1}{4}}]$. Here $T$ is the temperature of the system, ${\ensuremath{\rho}}_{0}$ is the density of states at the Fermi level, $\ensuremath{\lambda}$ is a dimensionless constant, and ${\ensuremath{\alpha}}^{\ensuremath{-}1}$ is the distance for exponential decay of the wave functions. We rederive these results, relating $\ensuremath{\lambda}$ to the critical density of a certain dimensionless percolation problem, and we estimate $\ensuremath{\lambda}$ to be approximately 16. The applicability of the model to experimental observations on amorphous Ge, Si, and C is discussed.

1,458 citations