In this work, we present the investigation of temperature dependent hall measurement of the ultra thin VO$_2$ films grown on Si/SiO$_2$ substrate. Experimental results suggest that electrons are the predominant carrier both in the semiconducting and metallic phases. The decrease of the resistivity with increasing temperature is mainly caused by the increase in the number density of charge carriers. The temperature dependence of the carrier concentration indicates the VO$_2$ films has a band gap of 0.40$\pm$0.09 $ev$ in the semiconducting phase. Analysis of hall effect data based on a composite cube model suggests that the sample has some untransitional phase with a length that is 1/4 of the grains.

The electronic and atomic structures of amorphous transparent tin oxides have been investigated by a combination of X-ray spectroscopy and atomistic calculations. Crystalline SnO is a promising p-type transparent oxide semiconductor due to a complex lone-pair hybridization that affords both optical transparency despite a small electronic band gap and spherical s-orbital character at the valence band edge. We find that both of these desirable properties (transparency and s-orbital valence band character) are retained upon amorphization despite the disruption of the layered lone-pair states by structural disorder. We explain the anomalously large band gap widening necessary to maintain transparency in terms of lone-pair stabilization via atomic clustering. Our understanding of this mechanism suggests that continuous hole conduction pathways along extended lone pair clusters should be possible under certain stoichiometries. Moreover, these findings should be applicable to other lone-pair active semiconductors.

Some transfer students have significant challenges in adapting to the pace and depth of a competitive four-year University. According to the National Student Clearinghouse Research Center, only 60% of transfer students from community colleges have earned their baccalaureate degree four years after transferring. In this paper, we present our program designed to increase the success rate of transfer students. Our goal is to continue Binghamton University's tradition of providing an effective collegiate learning environment for all, and particularly, to increase the success rate of the transfer students in STEM fields.

Amorphous In-Ga-Zn-O is an important oxide semiconductor in advanced display technologies. Despite its importance, little has been reported on the thermal and elastic properties of this material. Here, the temperature dependence of the thermal conductivity, shear modulus, and internal friction of a-InGaZnO 4 and a-In 2 Ga 2 ZnO 7 films are presented. The thermal conductivity of a-In 2 Ga 2 ZnO 7 , measured from 100 K to room temperature, was found to be larger than that of a-InGaZnO 4 over the entire temperature range. At room temperature the thermal conductivities were 1.9 W/m K and 1.4 W/m K for the a-In 2 Ga 2 ZnO 7 and a-InGaZnO 4 films, respectively. The shear modulus and internal friction of these films were measured in the temperature range of 340 mK to 65 K. At 4.2 K the shear modulus of the a-InGaZnO 4 and a-In 2 Ga 2 ZnO 7 films was 44 GPa and 42 GPa, respectively. The internal friction of thin films at each composition exhibited a temperature dependence and magnitude that is in agreement with that observed in all amorphous solids. As the self-heating effect is of concern in the development of amorphous In-Ga-Zn-O based thin film transistors on low thermal conductivity substrates, a thermal model of such a device utilizing a-In 2 Ga 2 ZnO 7 or a-InGaZnO 4 as the active layer was explored. It was found that the temperature increase of the thin film transistor channel is essentially independent of the thermal conductivity of the active layer.

The stability of kesterite Cu2ZnSnS4 (CZTS) under a range of compositions leads to the formation of a number of stable defects that appear to be necessary for high efficiency photovoltaic applications. In this work, the impact of the presence of these defects on the thermal conductivity of CZTS thin films has been explored. Thermal conductivities of CZTS thin films, prepared by pulsed laser deposition with differing compositions, were measured from 80 K to room temperature using the 3ω-method. The temperature dependence of the thermal conductivity indicates that the phonon mean free path is limited by strain field induced point defect scattering from sulfur vacancies in sulfur deficient thin films. The sulfurization of these films in a 10% N2 + H2S ambient at 500 °C increased the sulfur content of the films, reducing the concentration of sulfur vacancies, and produced a negligible change in grain size with an unexpected factor of 5 increase in phonon boundary scattering. This, along with anisotropies in the x-ray diffraction peak profiles of the sulfurized films, suggests that the phonon mean free path in sulfurized films is limited by the presence of cation exchange induced stacking faults. The resulting room temperature thermal conductivities for sulfurized and sulfur deficient thin films were found to be 4.0 W/m K and 0.9 W/m K, respectively.

Semiconductors with low lattice thermal conductivity are important in the search for more efficient thermoelectric materials. The thermal conductivity of nanocrystalline (<7 nm) Zn3P2, fabricated in thin film form by pulsed laser deposition, was measured from 80 K to 294 K. The thermal conductivity of the film showed weak temperature dependence in this temperature range and at 294 K had its highest value of 0.49 W/m K. Although Zn3P2 and its family of isomorphic compounds are known to have intrinsically low thermal conductivity, at room temperature the thermal conductivity of this nanocrystalline film is 25% smaller than the calculated minimum thermal conductivity for Zn3P2. Analyzing the thermal conductivity data with the Callaway model revealed that the data could be well fit by considering only boundary scattering and point defect scattering. The boundary scattering length was in good agreement with the film's average crystallite size of 4.1 nm and the magnitude of the point defect scattering required the formation of Vzn-Zni pairs from approximately 23% of the Zn sites. It is believed that a large number of point defects are responsible for the intrinsically low thermal conductivity of bulk Zn3P2 and therefore the exceptionally low thermal conductivity found in the present study results from the nanometer dimensions of the crystallites. As previous studies have reported high Seebeck coefficients and electronic properties that are insensitive to grain boundaries in Zn3P2, the low thermal conductivity observed in the present study suggests that nanocrystalline Zn3P2 should be further explored for use in thermoelectric applications. (C) 2016 Elsevier B.V. All rights reserved.

Flexible glass is one of the most promising innovations in the 21st century. Its applications in roll-to-roll (R2R) based manufacturing can yield low cost, conformable, and transparent electronics. In this work, we introduce electronic interposer substrates consisting of multiple metal-insulator layers of subtractively processed single micron metal circuit lines as well as high performance IGZO thin film transistors fabricated on Corning® Willow® Glass. All processes are compatible with R2R patterning and fabrication.

Amorphous indium gallium zinc oxide (a‐IGZO) is the archetypal transparent amorphous oxide semiconductor. Despite the gains made with a‐IGZO over amorphous silicon in the last decade, the presence of deep subgap states in a‐IGZO active layers facilitate instabilities in thin film transistor properties under negative bias illumination stress. Several candidates could contribute to the formation of states within the band gap. Here, we present evidence against In+ lone pair active electrons as the origin of the deep subgap features. No In+ species are observed, only In0 nano‐crystallites under certain oxygen deficient growth conditions. Our results further support under coordinated oxygen as the source of the deep subgap states.

Microfabrication is a critical area to many branches of science and engineering. However, to many students accustomed to seeing transistors as things that come in a lab kit, it is an obscure subtopic of their discipline. Beginning in 2009, the authors undertook a broad multidisciplinary approach to bring microfabrication into all aspects of the Binghamton University science and engineering curriculum. This program was coupled with a comprehensive assessment activity to evaluate the program's effectiveness and continuously improve it year by year. This paper reports the details of the implementation process, the techniques that were found to bring a hands-on experience to large classes, and the lessons learned from the assessments of this program to make this topic a mainstream part of engineering and science education.

Molecular Dynamics (MD) simulations of heat flow in the composite systems consisting of aluminum oxide nanostructures surrounded by polyethylene oxide were performed using known forcefields with consistent treatment of covalent (polymer) and ionic (nanoparticles) components. A reverse non-equilibrium molecular dynamics (RNEMD) method [implemented in open source MD Simulator LAMMPS was utilized to impose a temperature gradient and obtain the values of thermal conductivity. Several simulation boxes containing layers (4 nm and 20 nm width) and spheres (3 nm and 6 nm radii) of aluminum oxide surrounded by polyethylene oxide have been built, equilibrated and subjected to RNEMD. The sizes of the boxes varied from 10/15 nm × 10/15 nm × 45/200 nm. The boxes contained 0.6*106 to 3*106 atoms. An enhancement of effective thermal conductivity from 0.3 W/m·K (for pure polymer) up to 1.1 W/m·K was achieved for the composites containing multiple 20 nm layers of aluminum oxide. The value of interfacial thermal resistance at the aluminum oxide/polymer interface obtained from the simulations was approximately 5*10-9 m2K/W. Temperature profiles from RNEMD atomistic simulations were compared to known bulk models. Patterns of time averaged local heat flux in different components of the composite systems were calculated.

The origin of the deep subgap states in amorphous indium gallium zinc oxide (a-IGZO), whether intrinsic to the amorphous structure or not, has serious implications for the development of p-type transparent amorphous oxide semiconductors. We report that the deep subgap feature in a-IGZO originates from local variations in the oxygen coordination and not from oxygen vacancies. This is shown by the positive correlation between oxygen composition and subgap intensity as observed with X-ray photoelectron spectroscopy. We also demonstrate that the subgap feature is not intrinsic to the amorphous phase because the deep subgap feature can be removed by low-temperature annealing in a reducing environment. Atomistic calculations of a-IGZO reveal that the subgap state originates from certain oxygen environments associated with the disorder. Specifically, the subgap states originate from oxygen environments with a lower coordination number and/or a larger metal-oxygen separation.

The origin of the almost unique combination of optical transparency and the ability to bipolar dope tin monoxide is explained using a combination of soft and hard X-ray photoemission spectroscopy, O K-edge X-ray emission and absorption spectroscopy, and density functional theory calculations incorporating van der Waals corrections. We reveal that the origin of the high hole mobility, bipolar ability, and transparency is a result of (i) significant Sn 5s character at the valence band maximum (due to O 2p–Sn 5s antibonding character associated with the lone pair distortion), (ii) the combination of a small indirect band gap of ∼0.7 eV (Γ–M) and a much larger direct band gap of 2.6–2.7 eV, and (iii) the location of both band edges with respect to the vacuum level. This work supports Sn2+-based oxides as a paradigm for next-generation transparent semiconducting oxides.

The thermal conductivity of 100 nm zinc oxide nanowires embedded in silica aerogel was measured using the 3ω method over a temperature range of 150 K to 300 K. Compared to 100 nm ZnO nanowires alone, the thermal conductivity of the nanocomposite was reduced by over an order of magnitude throughout this temperature range. We attribute this reduction to the scattering of ballistic phonons at the nanowire surface and the subsequent emission of and transport of energy by the scattered phonon into the silica aerogel, as predicted by the diffuse mismatch model.