Search

SnTe is receiving a lot of attention as a topological crystalline insulator. Herein, SnTe films are grown directly on GaAs (100) substrates by molecular beam epitaxy. The surface morphology and electronic properties are measured by atomic force microscopy and Hall effect measurement, respectively. Considering previous X‐ray diffraction results, the samples grown with high beam‐intensity ratios show hexagonal Te segregation in the films, which deteriorates the surface morphology and decreases the conductivity. By suppressing the supply of Te, better surface morphology and electrical properties are obtained. [ABSTRACT FROM AUTHOR]

A comprehensive investigation on the low-field 2-DEG mobility in InxAl1-xN/AlN/GaN heterostructure has been made through Hall experimental and numerical calculation based on an ensemble Monte Carlo (MC) approach. Hall measurement on a lattice-matched (LM) In0.18Al0.82N/AlN/GaN heterostructure grown by metal-organic chemical vapor deposition (MOCVD) has been carried out as a function of temperature ranging from 77 to 405 K. A more rigorous model is presented taking both inter- and intra-subband scattering into account. The scattering rates are derived from the results of the electron density, the quantized energy levels, and the corresponding wave functions based on the self-consistent solutions of Poisson’s and Schrödinger’s equation given in our previous work. We confirm that the interface scattering process dominates the mobility within the low temperature (77–130 K), as increasing of the temperature, the highly inelastic scattering caused by partial occupation of the higher subband is responsible for the rapid degradation of the 2-DEG mobility. The role of surface morphology and indium fraction of the heterostructure on the dependence of the 2-DEG mobility have been clarified qualitatively in detail. The calculated results are widely compared with the published literature and our experimental finding. A reasonable agreement is achieved. [ABSTRACT FROM AUTHOR]

Zinc selenide (ZnSe) thin films with various thicknesses were grown on ultrasonically clean glass substrates using vacuum evaporation of 99.99% pure ZnSe powder. Thickness dependence of the structural, optical and electrical properties was thoroughly investigated. X-ray diffraction (XRD) analyses revealed that (110) ZnSe plane is the dominant crystal plane for all the fabricated films. Both dislocation density and micro-strain go down with the increase in film thickness, indicating lower lattice defects and improvement in crystallinity at higher film thickness. Transmittance spectra show that all the films have almost linear upward tendency of transmittance in near-infrared region and small fluctuations in visible region for higher-thickness films. With the increase in film thickness, the optical bandgap increases and also an increasing tendency of dielectric constant was observed. Studies of electrical properties showed a sharp increase in carrier mobility and concentration with film thickness. As the film thickness increases from 30 to 90 nm, the carrier mobility goes up from 255 to 1250 cm2/VS and the carrier concentration increases from 2.14 × 1018 to 9.37 × 1018 cm−3. The electrical transport properties of the deposited thin films were explained in terms of scattering of the charge carrier. [ABSTRACT FROM AUTHOR]

Partially nitrided LiCoO2 thin films with stoichiometric contents of Li and Co were fabricated on sapphire substrates using an ethanol solution. The precursor films were formed by spin-coating. By thermal treatment of' the precursor films at 350, 450, 550 and 650°C for 30 min in air, four kinds of LiCoO2 thin films were obtained. That annealing of the precursor film at 650°C resulted in the nucleation of Co3O4 from the layered LiCoO2, which has been confirmed by the Raman spectrum. Three X-ray photoelectron spectroscopy peaks observed at 527.9 eV, 402.1 eV, and 396.2 eV were newly assigned to the O-Co4+, N-Co4+, and N-Co2+ bonds, respectively, using a peak-analysis technique. The resistivity of the layered LiCoO2 thin film fabricated at 650°C was measured to be 1.2 Ω cm. [ABSTRACT FROM AUTHOR]

γ-MnS thin films were prepared on glass substrate by spray pyrolysis method at 280 °C. The optical constants and thickness of the films were extracted using the pattern search optimization technique in combination with a seed preprocessing procedure (spPS). Refractive index dispersion of the films was analyzed by using the concept of the single oscillator model. The values of the oscillator energy, E0, and the dispersion energy, Ed, were determined as 8.83 eV and 5.65 eV, respectively. The analysis of the optical properties of the γ-MnS film showed a direct transition with energy band gap of 2.74 eV. Utilizing Hall Effect measurement, we have determined values of the resistivity p which equals to 1150 Ocm. The positive value of hall coefficient showed a p-type in nature of the obtained thin film. The maximum of photocurrent density estimated by Yablonovitch limit is equal to 46 mA/cm2. [ABSTRACT FROM AUTHOR]

The course "Materials in Electrical Engineering" is a core course in the Mechatronics curriculum at the Faculty of Technical Sciences, University of Novi Sad, Serbia. In the past, this course was comprehensive and mainly theory-based. Teaching methods used in this course had not been changed for many years, and were mainly based on a traditional approach. They were therefore often outdated, and boring for students. In addition, the lack of modern materials characterization equipment was a significant weakness of the course in its early stages. This paper presents the main aspects of the modified course, which features a greater inclusion of modern equipment in its teaching methodology; in particular it produces the Hall effect measurement system as an indispensable characterization technique in education, research and in the semiconductor industry. This paper also describes how students can be taught to use the Hall effect measurement system to determine the structural and electrical characteristics of different materials. Finally, students' feedback and observations on the modified course and the applied teaching methodology are discussed. [ABSTRACT FROM AUTHOR]

Ternary Ta2NiSe5 is a novel electronic material having the property of an excitonic insulator at room temperature. The electrical properties of Ta2NiSe5 have not been elucidated in detail. We discuss the electronic properties in Ta2NiSe5 films and the formation of heterojunctions. Hall effect measurements showed p-type conductivity. The activation energies estimated from the temperature dependence of the carrier concentration were seen to be 0.17 eV and 0.12 eV, at approximately 300 and 400 K, respectively. It was observed that carrier generation behavior changes at the critical temperature of the excitonic insulator state (328 K). The temperature dependence of the Hall mobility below the critical temperature nearly follows the bell-shaped curves for conventional semiconductor materials. A MoS2/Ta2NiSe5 van der Waals heterojunction was fabricated using the transfer method. Rectification characteristics, which depend on the gate bias voltage, were obtained. The barrier height at the MoS2/Ta2NiSe5 heterointerface and the on/off ratio could be modulated by applying a gate bias voltage, suggesting that the carrier transport was exhibited in band-to-band flow. Our demonstration suggests that the knowledge of Ta2NiSe5 increased as an electronic material, and diode performance was successfully achieved for the electronic device applications. [ABSTRACT FROM AUTHOR]

Narrow band-gap semiconductors, namely ternary InAsSb alloys, find substantial technological importance for mid-infrared application as photodetectors in medical diagnostics or environmental monitoring. Thus, it is crucial to develop electrical contacts for these materials because they are the fundamental blocks of all semiconductor devices. This study demonstrates that electroplated gold contacts can be considered as a simple and reliable metallization technology for the electrical-response examination of a test structure. Unalloyed electroplated Au contacts to InAsSb exhibit specific contact resistivity even lower than vacuum-deposited standard Ti–Au. Moreover, temperature-dependent transport properties, such as Hall carrier concentration and mobility, show similar trends, with a minor shift in the transition temperature. It can be associated with a difference in metallization technology, mainly the presence of a Ti interlayer in vacuum-deposited contacts. Such a transition may give insight into not only the gentle balance changes between conductivity channels but also an impression of changing the dominance of carrier type from p- to n-type. The magnetotransport experiments assisted with mobility spectrum analysis clearly show that such an interpretation is incorrect. InAsSb layers are strongly p-type dominant, with a clear contribution from valence band carriers observed at the whole analyzed temperature range. Furthermore, the presence of thermally activated band electrons is detected at temperatures higher than 220 K. [ABSTRACT FROM AUTHOR]

The capability of graphene-based biosensors used to detect biomolecules, such as DNA and cancer marker, is enormously affected by the quality of graphene. In this work, high quality and cleanness graphene were obtained by CVD based on acetic acid (AA) and ammonium persulfate (AP) pretreated copper foil substrate. Hall effect devices were made by three kinds of graphene which were fabricated by CVD using no-treated copper foil, AA pre-treated copper foil and AP pre-treated copper foil. Hall effect devices made of AA pre-treated copper foil CVD graphene and AP pre-treated copper foil CVD graphene can both enhance the sensitivity of graphene-based biosensors for DNA recognition, but the AA pre-treated copper foil CVD graphene improves more (≈4 times). This may be related to the secondary oxidation of AP pre-treated copper foil in the air due to the strong corrosion of ammonium persulfate, which leads to the quality decrease of graphene comparing to acetic acid. Our research provides an efficient method to improve the sensitivity of graphene-based biosensors for DNA recognition and investigates an effect of copper foil oxidation on the growth graphene. [ABSTRACT FROM AUTHOR]