Temperature dependence of concentrations and mobilities in thin bismuth films

The resistivity, Hall coefficient and magnetoresistance of thin bismuth films were measured at various temperatures (80–300 K) and thicknesses (0.1–3 μm). The mobilities and concentrations of the free electrons and holes were calculated from the experimental data using an anisotropic two-carrier model. Four approaches to the calculation were applied and the results were compared with one another. It was found that the electron and hole concentrations are approximately equal.     

Structure and optical properties of ZnO:V thin films with different doping concentrations

A series of ZnO thin films doped with various vanadium concentrations were prepared on glass substrates by direct current reactive magnetron sputtering. The results of the X-ray diffraction (XRD) show that the films with doping concentration less than 10 at.% have a wurtzite structure and grow mainly along the c-axis orientation. The residual stress, estimated by fitting the XRD diffraction peaks, increases with the doping concentration and the grain size also has been calculated from the XRD results, decreases with increasing the doping concentration. The surface morphology of the ZnO:V thin films was examined by SEM. The optical constants (refractive index and extinction coefficient) and the film thickness have been obtained by fitting the transmittance. The optical band gap changed from 3.12 eV to 3.60 eV as doping concentration increased from 1.8 at.% to 13 at.% mol. All the results have been discussed in relation with doping concentration.     

Lasing action in organic semiconductor thin films

Lasing action in optically pumped thin films of organic semiconductors has recently been demonstrated in a variety of materials employing a variety of cavity configurations. The excitation intensities required for lasing in optically pumped films are comparable to the electrical current densities achievable in light emitting devices based on these materials, opening the door to the possible realization of organic diode lasers. However, the design of diode laser structures is complicated by the relatively low charge carrier mobilities of organics. It has also been shown that the optical properties of organic films under electrical excitation are affected by the formation of polarons, imposing yet another obstacle for realization of these devices. The continuing research on organic diode lasers is motivated by the unique properties of these devices, such as narrow spectral emission linewidth and the temperature independence of laser output power and emission wavelength, which may be advantageous in a number of applications.     

Complicated quasi-particle complexes in thin semiconductor films

The formation of complicated quasi-particle complexes (mainly the biexciton ions, the exciton molecules and exciton-donor neutral complexes) in thin semiconductor films has been investigated theoretically. Analytical expressions have been obtained for the dissociation energies of these quasi-particle complexes as functions of the ratio of the effective mass of the electron to that of the hole. The conditions for the formation of such complexes are shown to be more favourable in thin films than in bulk semiconductors.

The influence of a homogeneous magnetic field on the dissociation energy of biexciton ions in a bulk semiconductor is also investigated.     

Behaviors of carrier concentrations and mobilities in indium-tin oxide thin films by DC magnetron sputtering at various oxygen flow rates

The behaviors of the carrier concentrations and mobilities of indium-tin oxide (ITO) thin films, prepared by DC magnetron sputtering at the various oxygen flow rates, were investigated by means of the Hall technique. The relationship between the carrier concentrations and mobilities along the oxygen flow rates had two distinct features: (i) in the optimum oxygen region to 1.25 O₂/Ar vol%, the carrier mobilities increased as the carrier concentrations decreased with the oxygen flow rates and (ii) in the excess oxygen region roughly above 1.25 O₂/Ar vol%, both the carrier concentrations and mobilities decreased with the increases in the oxygen flow rates.The continuous decreases in the carrier concentrations with the oxygen flow rates were due to filling the oxygen vacancies and deactivating the Sn donor by the overflowing oxygens. The behaviors of the carrier mobilities were affected by two different scattering mechanisms of (i) the ionized impurity scattering in the optimum oxygen region and (ii) the neutral defect scattering and the negatively charged oxygen scattering in the excess oxygen region.     

Charge carrier and spin doping in ZnO thin films

Recent efforts on doping ZnO films for charge and spin functionality are reviewed, focusing on chemical doping for charge and spin device formation. Discussion includes the behavior of phosphorus as an acceptor and magnetism in transition metal-doped ZnO. Evidence for p-type behavior in phosphorus-doped (Zn,Mg)O grown by pulsed laser deposition is presented. The magnetic properties of ZnO co-doped with Mn and Sn are also discussed.     

Microstructural evolution of oxides and semiconductor thin films

This review article introduces the preparation methodologies and the microstructural characteristics of semiconductor thin films, including SnO₂ thin films, Au/Ge bilayer films, and Pd-Ge alloy thin films, and metal oxides, including SnO, SnO₂, Mn₂O₃ and Mn₃O₄ nanocrystals which can be in the form of nanoparticles, nanowires, nanorods, and nanofractals. Firstly, the preparation methodologies and the microstructural characteristics of tin oxides have been investigated in detail and described in Section 2. Secondly, the crystallization of amorphous Ge, and the formation of nanocrystals and compounds developed with improved micro- and nanostructured features are described in Section 3. Thirdly, a novel selective synthesis route for various morphologies of manganese oxides nanocrystals, including nanoparticles, nanorods and nanofractals, and their unique microstructural characteristics are presented in Section 4. Intricate fundamental properties of manganese oxides nanocrystals are studied in detail. To sum up, it is expected that the fabrication methodologies developed and the knowledge of microstructural evolution gained in semiconductor thin films, including SnO₂ thin films, Au/Ge bilayer films, and Pd-Ge alloy thin films, and metal oxides, including SnO, SnO₂, Mn₂O₃ and Mn₃O₄ nanocrystals in the forms of nanoparticles, nanowires, nanorods, and nanofractals, will provide an important fundamental basis underpinning further interdisciplinary (physics, chemistry and materials science) research in this field leading to promising exciting opportunities for future technological applications involving these oxide and thin film materials.     

Electrodeposition and characterization of CdSe semiconductor thin films

The electrodeposition of cadmium selenide alloy on glassy carbon and gold electrodes has been studied by electrochemical techniques. Potentiostatic I-t transients were recorded to obtain the nucleation mechanism, while cyclic voltammetry was used to characterize the system. Structural information on the electrodeposited layers was obtained by X-ray diffraction. The experimental results clearly show that the deposition of cadmium selenide alloy on glassy carbon and gold electrodes is a diffusion-controlled process. The nucleation is progressive, and the number of nucleation sites decreases with increasing bath temperature. The deposition of CdSe alloy results in well-defined crystals with hexagonal shape. The films were characterized by optical absorption and electrical resistivity measurements. Films showed a direct band gap of 3.56 eV.     

氢敏元件的种类及半导体薄膜材料在其中的应用

随着氢燃料电池技术在汽车应用中的日益完善,对高性能氢敏元件的需求也更加迫切。本文介绍了采用不同工作原理制备的氢敏元件的种类,着重描述了半导体薄膜材料的工作原理和改性途径,并针对我国目前研究较少的Ga2O3新型薄膜材料进行了较为详细的综合论述。     

Electrical conduction mechanisms in thin amorphous semiconductor films

An account is given of the different conduction mechanisms possible in thin amorphous semiconductor films. Special attention is paid to the low temperature regime where variable range hopping between states near the Fermi level is supposed to be most important. An attempt is made to assess the significance of fits of the conductivity versus temperature relation to the much-used T^{-$\text{1}\text{4}$} relation proposed by Mott.     

Nanoscale rapid melting and crystallization of semiconductor thin films

The current study details nanosecond laser-based rapid melting and crystallization of thin amorphous silicon (a-Si) films at the nanoscale using two different optical near-field processing schemes. Both apertureless and tapered fiber near-field scanning optical microscope probes were utilized to deliver highly confined irradiation on the target surface. The various modification regimes produced as a result of the rapid a-Si melting and crystallization transformations were shown to critically depend on the applied laser fluence. Consequently, the crystallized pattern morphology and feature size could be finely controlled. High energy density was observed to impart ablation surrounded by a narrow melt ring. At much lower incident laser energy density, single nanostructures with a lateral dimension of approximately 90 nm were defined.     

p型掺杂ZnO薄膜的研究进展

近年来,随着对ZnO的光电性质及其在光电领域应用的开发研究,制备可靠稳定的低阻p型ZnO薄膜成为研究热点之一。本文论述了p型ZnO薄膜制备的难点及其解决方法,综述了其最新研究进展,并对p型ZnO的研究进行了展望。     

介电/半导体功能集成薄膜的制备和特性调控

介电/半导体功能集成薄膜,主要是指将具有电、磁、声、光、热等功能特性的介电功能材料(主要是氧化物类介电功能材料)与硅、砷化镓或氮化镓等典型半导体类功能材料,以单层薄膜或多层薄膜的形式生长(甚至外延生长)在一起而形成的人工新材料,这类新材料有可能具有多功能一体化和功能特性之间的相互调制及耦合等特点,可望在新型电子和光电子器件中获得应用.介绍了介电/半导体功能集成薄膜产生的背景;从集成铁电薄膜与器件、HK/半导体集成薄膜与器件以及极性氧化物/GaN功能集成薄膜与器件等3个方面,分别介绍了介电/半导体功能集成薄膜的应用;概括介绍了介电/半导体功能集成薄膜的制备方法及特性调控.     

ZnO薄膜的p型掺杂研究进展

ZnO作为重要的第三代半导体材料在光电领域具有广泛的应用前景因而引起越来越多的关注,ZnO薄膜的p型掺杂是实现ZnO基光电器件的关键,也是ZnO材料的主要研究课题.本文论述了ZnO薄膜P型转变的难点及其解决方法,概述了ZnO薄膜p型掺杂的研究现状,提出了有待进一步研究的问题.     

Application of electroreflectance analysis for organic semiconductor thin films

Many organic semiconductors with conjugate bond structure possess photoconductivity. Conduction mechanism of organic materials exhibits ‘dualism’ since both intramolecular as well as inter-molecular aspects are involved in the excitation, absorption and transport of charge carriers. Modulation spectroscopy promises to be the most accurate method for analysis of organic photoconductors, especially of thin films. In this technique a periodic perturbation is applied to the material under study and the effect of the perturbation is separated from reflection or absorption while scanning through a given wavelength range by use of lock-in phase sensitive detection method. In electromodulation, particularly in electrolyte electromodulation, the applied field on the material produces changes in the dielectric function which corresponds to the change in reflectance. When the applied field is low the line-shape of spectrum is third-derivative like in comparison with the unmodulated reflectance spectrum. Using Aspnes three-point method the transitions corresponding to critical points can be determined. When the field is intermediate Franz-Keldysh oscillations, which are dc bias dependent, appear on the higher energy side of the transition energy from which the role of intra-molecular as well as intermolecular aspects in conduction mechanism can be understood and the carrier concentration could be determined. Though the electroreflectance method has been developed for inorganic semiconductors, it could be effectively applied for organic/molecular semiconductors as well if the constituent molecules are assumed to be the lattices. The study of organic photoconductors is very important since they are more and more promising especially in photocopying, photovoltaic and solar cells.     

Compositional analysis of semiconductor thin films using electroanalytical techniques

Thin films of CdSe, CdTe, ZnSe and InTe prepared on glass substrates by vacuum evaporation were analysed for stoichiometry using the techniques of d.c. polarography, cyclic voltammetry and chronoamperometry. The electroanalytical results are compared with data obtained using energy-dispersive analysis with X-rays.