Enhancement of photosensitivity in bismuth doped Cu2ZnSnS4 thin films

In this paper, the effect of bismuth doping on the structural, morphological, optical and electrical properties of Cu₂ZnSnS₄ (CZTS) films has been investigated. The undoped and bismuth doped CZTS films (0, 0.5, 1, 1.5 and 2 mol%) were deposited on glass substrates by solution based method. The XRD result shows a significant improvement in the crystallinity of the films with increase in bismuth concentration. The Raman spectra of the films show the dominant peak at 334 cm^–1 corresponding to A₁ vibrational mode of CZTS kesterite phase. The FESEM micrographs of the films show an enhancement in the grain size and densification with the addition of bismuth ion concentration. The optical bandgap of the films was found to vary (1.59–1.40 eV) with the doping of bismuth ions. The I –V characteristics indicate twofold increment in the photoconductivity for the bismuth doped CZTS films under 100 mW/cm² illumination suggesting their potential application in photovoltaic devices. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Hall effect and pinning regimes in thin films doped with nanoparticles

Hall effect and flux pinning in YBa₂Cu₃O_6+x (YBCO) thin films doped with BaZrO₃ (BZO) nanoparticles is investigated. The results show that sign reversal of the Hall coefficient from positive hole-like to negative electron-like occurs in vortex-liquid regime of undoped and BZO-doped YBCO films. With increasing BZO concentration the amplitude of the negative Hall effect is suppressed while the temperature position of the anomalous Hall effect does not depend significantly on doping level. In addition, it is shown that Hall conductivity increases non-monotonically with increasing BZO doping. These results support a model where BZO at low doping concentration induces point pinning centres turning to strong columnar pinning defects in films doped with 4% BZO.     

Electrical properties of antimony-doped p-type Hg0.78Cd0.22Te liquid-phase-epitaxy films

Hall measurements have been performed on antimony-doped p-type Hg_0.78Cd_0.22Te LPE (Liquid-Phase-Epitaxy) films between 20 and 150 K. The ionization energy of isolated shallow acceptors was estimated to be about 11 meV. From the analysis of the Hall coefficient and the hole mobility data, we found that compensation in the films is not enough to explain the typically low hole mobility at low temperatures.     

The effect of hydrogen on the electrical properties of n-type Pb0.9Cd0.1Te thin films

Measurements of the Hall coefficient and the d.c. conductivity were made on flash evaporated n-type Pb_0.9Cd_0.1Te epitaxial films exposed to molecular hydrogen gas at high pressures (upto 500 psi) in the temperature range 77–300 K. It has been found that the effect of hydrogen on the films is to reduce the concentration of the extrinsic carriers and to increase their mobility. It is believed that hydrogen gas removes cadmium ions and neutral cadmium atoms from these films.     

Preparation and properties of co-evaporated bismuth telluride [Bi2Te3] thin films

Thin films of bismuth telluride have been prepared by the reactive evaporation method. Film properties, such as conductivity, Hall effect, and thermoelectric power were studied in the temperature range from liquid nitrogen to 350 K. The films prepared were of n-type with a carrier concentration of 1.25 x 10²⁰ at room temperature. The temperature dependence of the Hall mobility is found to be T^?1.8 indicating lattice scattering.     

Effects of laser irradiation energy density on the properties of pulsed laser deposited ITO thin films

The properties of indium tin oxide (ITO) thin films, deposited at room temperature by simultaneous pulsed laser deposition (PLD), and laser irradiation of the substrate are reported. The films were fabricated from different Sn-doped In₂O₃ pellets at an oxygen pressure of 10 mTorr. During growth, a laser beam with an energy density of 0, 40 or 70 mJ/cm² was directed at the middle part of the substrate, covering an area of ∼1 cm². The non-irradiated (0 mJ/cm²) films were amorphous; films irradiated with 40 mJ/cm² exhibited microcrystalline phases; and polycrystalline ITO films with a strong 〈111〉> preferred orientation was obtained for a laser irradiation density of 70 mJ/cm². The resistivity, carrier density, and Hall mobility of the ITO films were strongly dependent on the Sn doping concentration and the laser irradiation energy density. The smallest resistivity of ∼1×10^-4 Ω cm was achieved for a 5 wt % Sn doped ITO films grown with a substrate irradiation energy density of 70 mJ/cm². The carrier mobility diminished with increasing Sn doping concentration. Theoretical models show that the decrease in mobility with increasing Sn concentration is due to the scattering of electrons in the films by ionized centers. PACS 81.15.Fg; 73.61.-r; 73.50.-h     

Conductivity and Hall effect measurements in doped polyacetylene

Conductivity and Hall effect measurements are reported for polyacetylene films heavily doped with AsF₅. The Hall coefficient is anomalously small, however, it is p-type and relatively temperature insensitive in the range 4–300 K indicative of metallic conduction. The effects of film degration by heating and air exposure are also investigated.     

The effect of oxygen on the electrical properties of silicon

Interstitial oxygen present in solution, as detected by the 9 μ absorption band, increases the Hall mobility of electrons in n-type silicon crystals but decreases the Hall mobility of holes in p-type. These results are explained by the lattice strain produced via dissolved interstitial oxygen impurities. Results on samples saturated with oxygen and heat treated to cause precipitation of SiO₂ in the temperature range of 950–1250°C show that the SiO₂ particles decrease the values of Hall mobility compared to the initial values on samples without precipitates. Re-annealing causes the dissolution of the precipitates and recovery nearly to the initial values of the Hall coefficient.     

Structure and electrical transport properties of bismuth thin films prepared by RF magnetron sputtering

Bismuth thin films were prepared on glass substrates with RF magnetron sputtering and the effects of deposition temperature on surface morphology and their electrical transport properties were investigated. Grain growth of bismuth and the coalescence of grains were observed above 393 K with field emission secondary electron microscopy. Continuous thin films could not be obtained above 448 K because of the segregation of grains. Hall effect measurements showed that substrate heating yields the decrease of carrier density and the increase of mobility in exponential ways until 403 K. Resistivity of sputter deposited bismuth films has its minimum (about 0.7 × 10⁻³ Ω cm) in range of 403-433 K. Annealing of bismuth films deposited at room temperature was carried out in a radiation furnace with flowing hydrogen gas. The change of resistivity was not significant due to the cancellation of the decrease of carrier density and the increase of mobility. However, the abrupt change of electrical properties of film annealed above 523 K was observed, which is caused by the oxidation of bismuth layer.     

Optical, electrical and morphological properties of p-type Mn-doped SnO2 nanostructured thin films prepared by sol–gel process

SnO₂ thin films doped with various manganese concentrations were prepared on glass substrates by sol–gel dip coating method. The decomposition procedure of compounds produced by alcoholysis reactions of tin and manganese chlorides was studied by thermogravimetric analysis (TGA). The effects of Mn doping on structural, morphological, electrical and optical properties of prepared films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Hall effect measurement, Fourier Transform Infrared (FTIR) spectral analysis, UV–Vis spectrophotometry, and photoluminescence (PL) spectroscopy. The results of the X-ray diffraction show that the samples are crystalline with a tetragonal rutile structure and the grain size decreases with increasing the doping concentration. The SEM and AFM images demonstrate that the surface morphology of the films was affected from the manganese incorporation. The Sn_1?x Mn _x O₂ thin films exhibited electrically p-type behavior in doping level above x=0.035 and electrical resistivity increases with increase in Mn doping. The optical transmission spectra show a shift in the position of absorption edge towards higher wavelength (lower energy). The optical constants (refractive index and extinction coefficient) and the film thickness were determined by spectral transmittance and using a numerical approximation method. The oscillator and dispersion energies were calculated using the Wemple–DiDomenico dispersion model. The estimated optical band gap is found to decrease with higher manganese doping. The room-temperature PL measurements illustrate the decrease in intensity of the emission lines when content of Mn is increased in Mn-doped SnO₂ thin films.     

Preparation and characterization of Al doped ZnO thin films by PLD

This paper describes the effect of doping on the composition, surface morphology and optical, structural and electrical properties of Al doped ZnO thin films by pulsed laser deposition. SEM analysis shows that the crystalline nature of the deposited films decreases with an increase of Al doping concentration from 1% to 6%. In the AFM analysis, the surface roughness of the deposited films increases by increasing the doping concentration of Al. Al doping strongly influences the optical properties of the ZnO thin films. Optical transmittance spectra show a very good transmittance in the visible region (450–700 nm). The calculated optical band gap was found to be in the range from 3.405 to 3.464 eV. Structural analysis confirms that the increases of Al concentration decrease the crystallinity of the ZnO films and the particle size decreases from 45.7±0.09 to 28.0±0.02 nm. In the Raman analysis, the active mode of Al(=1%) doped ZnO films were observed at 434.81 cm⁻¹. The shifts of the active mode (_E2)$\left(E_2\right)$ show the presence of tensile stress in the deposited films. The electrical properties of the deposited films showed that the values of the Hall mobility was in the range between 2.51 and 10.64 cm²/V s and the carrier concentration between 15.7 and 0.78×10¹⁷ and the resistivity values between 1.59 and 10.97 Ωcm, depending on the doping concentration.     

Thermostatistical properties of a q-deformed bosonic exciton gas

We present the calculations of the electronic structure and transport properties on the filled-skutterudites LaFe₄Sb₁₂ and CeFe₄Sb₁₂ using the full-potential linearized augmented plane-wave method and the semi-classical Boltzmann theory. Our calculation indicates that LaFe₄Sb₁₂ and CeFe₄Sb₁₂ have the large density of states near the Fermi level. The obtained Seebeck coefficient and the magnetic susceptibilities are in good agreement with experimental results. It is found that n-type doping in the CeFe₄Sb₁₂ compound may be more favorable than p-type doping below 900 K and p-type doping in the CeFe₄Sb₁₂ compound may be more favorable than n-type doping above 900 K. It is also seen that n-type doping in the LaFe₄Sb₁₂ compound may be more favorable than p-type doping below 700 K and p-type doping in the LaFe₄Sb₁₂ compound may be more favorable than n-type doping above 700 K. Ultimately, we found that LaFe₄Sb₁₂ is more suitable for thermoelectric applications than CeFe₄Sb₁₂.     

The effect of Mg doping on the dielectric and tunable properties of Pb0.3Sr0.7TiO3 thin films prepared by sol–gel method

Mg doped Pb_0.3Sr_0.7TiO₃ (PST) thin films were fabricated by the sol–gel method on a Pt/Ti/SiO₂/Si substrate. The microstructure, surface morphology, dielectric and tunable properties of PST thin films were investigated as a function of Mg concentration. It is found that proper Mg doping dramatically improves the dielectric loss (0.0088 @ 1 MHz), furthermore, the crystallinity, dielectric constant, and tunability of films simultaneously decrease with the increase of Mg content. The 2 mol% Mg doped PST thin film shows the highest figure of merit (FOM) value of 36.8 for its the smallest dielectric loss and upper tunability. The dependence of Rayleigh coefficient on the doping concentration was examined, which indicated that the reduction of dielectric constant and tunability of films should be related to the $\mathrm{Mg}''_{\mathrm{Ti}}$ – $\mathrm{V}_{\mathrm{O}}^{\bullet\bullet}$ defect dipoles pinning the domain wall motion of residual polar clusters in PST.     

Realization of p-ZnO thin films by GaP codoping

An attempt has been made to realize p-ZnO by directly doping (codoping) GaP into ZnO thin films. GaP codoped ZnO thin films of different concentrations (1, 2 and 4 mol%) have been grown by RF magnetron sputtering. The grown films on sapphire substrate have been characterized by X-ray diffraction (XRD), Hall measurement, Photoluminescence (PL) and Energy dispersive spectroscopy (EDS) to validate the p-type conduction. XRD result shows that all the films have been preferentially oriented along (0 0 2) orientation. The decrease of full-width at half maximum (FWHM) with increase in GaP doping depicts the decrease in native donor defects. Hall measurement shows that among the three films, 2 and 4 mol% GaP doped ZnO shows p-conductivity due to the sufficient amount of phosphorous incorporation. It has been found that low resistivity (2.17 Ωcm) and high hole concentration (1.8×10¹⁸ cm⁻³) for 2% GaP codoped ZnO films due to best codoping. The red shift in near-band-edge (NBE) emission and donar-acceptor-pair (DAP) and neutral acceptor bound recombination (A°X) observed by room temperature and low temperature (10 K) PL, respectively, well acknowledged the formation of p-ZnO. The incorporated phosphorous in the film has been also confirmed by EDS analysis.     

Electron mobility of Sr1-xLaxTiO3 ceramics between 600 °C and 1300 °C

1-x La_xO₃ ceramics (0.003<x<0.40) were measured between 600 °C and 1300 °C. The density of electrons in the conduction band was determined from Hall and thermopower measurements. A chemical approach (Ti³⁺-titration) confirmed these results. The electron mobility was calculated by combining charge carrier density and conductivity data. The temperature dependence of the mobility obeys a power law. Its exponent varies from -1.5 for slightly doped samples (x=0.003) to -2.74 for lanthanum-rich samples (x=0.4) indicating a phonon scattering controlled transport behavior. The mobility data obtained from slightly doped ceramic samples agree very well with Hall mobilities found in undoped SrTiO₃ single crystals. Received: 22 January 1997/Accepted: 1 April 1997     

LPCVD a—Si薄膜的缺陷补偿和掺杂

本文通过ESR,σ_D,σ_Ph,SIMS和E_α等测量,对LPCVD方法生长的a-Si材料的掺杂、缺陷补偿和氢化作了研究,发现在这种材料中,虽然不存在可检测得出的氢含量,却仍然能够进行掺杂,特别是在重掺杂区,缺陷得到有效的补偿,E_F向带边移动。文中基于Street最近提出的关于a-Si掺杂的新观点,用缺陷补偿和化学配位等观点解释了没有氢情况下的掺杂机理。 关键词：     

掺杂水平对ZnO基变阻器电学性能的影响

根据相图规则设计、制备了三个系列不同Bi₂O₃与Sb₂O₃掺杂水平的ZnO基复合变阻器材料,研究了掺杂对氧化锌复合陶瓷电学性能的影响.研究发现,当Sb元素掺杂水平较低时,随着Sb₂O₃掺杂量的增加,所得氧化锌基变阻器材料漏电流的变化也很小,非线性系数(非线性系数α_L和击穿非线性系数α_B)将减小,而场强(场 关键词： 氧化锌 掺杂 复合陶瓷变阻器 电学性质     

Structure and electrical properties of Sb2Te3 and Bi0.4Sb1.6Te3 metastable phases obtained by HPHT treatment

We have obtained the metastable phase of the thermoelectric alloy Bi_0.4Sb_1.6Te₃ with electron type conductivity for the first time using the method of quenching under pressure after treatment at P=4.0 GPa and T=400–850 °C. We have consequently performed comparative studies with the similar phase of Sb₂Te₃. The polycrystalline X-ray diffraction patterns of these phases are similar to the known monoclinic structure α-As₂Te₃ (C2/m) with less monoclinic distortion, β ≈ 92°. We have measured the electrical resistivity and the Hall coefficient in the temperature range of T=77?450 K and we have evaluated the Hall mobility and density of charge carriers. The negative Hall coefficient indicates the dominant electron type of carriers at temperatures up to 380 K in the metastable phase of Sb₂Te₃ and up to 440 K in the metastable state of Bi_0.4Sb_1.6Te₃. Above these temperatures, the p-type conductivity proper to the initial phases dominates.     

Electronic-transport properties of unhydrogenated amorphous gallium arsenide

Summary Hall mobility, μ_H, and electrical conductivity, σ, of unhydrogenated amorphous-gallium-arsenide films, prepared by r.f. sputtering, have been measured. Conductivity as a function of temperature shows a variable-range hopping mechanism atT<260 K, while at high temperature, conductivity and Hall mobility are both thermally activated. The results are interpreted in terms of the presence of defect complexes due to an excess of Ga. The stoichiometry and the structure of the films are used to explain the behaviour and the values of μ_H. The values of the activation energy of the conductivity seem in agreement with theoretical calculations on the position of electronic states created by defect complexes in the mobility-gap of a-GaAs.     

On the electron mobility of δ layers in the presence of diamagnetic “ejection” of size-quantization levels

The Hall mobility of electrons is investigated as a function of the population of size-quantization subbands in the two-dimensional electron gas of a δ-doped layer in GaAs with constant total electron density N _s =3.2×10¹² cm⁻² (three initially filled subbands) at T=4.2 K. The population of the subbands is varied by diamagnetic “ejection” of size-quantization levels (i.e., pushing them over the Fermi level) by a magnetic field oriented parallel to the plane of the δ-doped layer. The measurements are made in magnetic fields making small angles (5°) with the plane of the doping. The magnetic field component normal to the plane was used to measure the Hall mobility and density. It is found that the measured Hall mobility as a function of the ejecting magnetic field has a distinct maximum. This maximum is due to an increase in the electron mobility in the first subband (the ground subband is assigned the index 0) and electron redistribution between subbands with in increasing ejecting magnetic field parallel to the plane of the δ layer. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 11, 704–708 (10 December 1997)