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Atomic resolution scanning/transmission electron microscopy (S/TEM) and energy-dispersive x-ray (EDX) analysis were used to determine the effects of annealing at 800–1000 °C in air on Ga2O3 films grown on (100) MgAl2O4 at 650 °C via metal-organic chemical vapor deposition. Annealing resulted in the diffusion of Mg and Al into the films concomitantly with the transformation of β-Ga2O3 to γ-Ga2O3 solid solutions. The minimum atomic percent of Al + Mg that corresponded with the transformation was ∼4.6 at. %. Analyses of atomic-scale STEM images and EDX profiles revealed that the Al and Mg atoms in the γ-Ga2O3 solid solutions occupied octahedral sites; whereas the Ga atoms occupied tetrahedral sites. These site preferences may account for the stabilization of the γ-Ga2O3 solid solutions. [ABSTRACT FROM AUTHOR]

The Schottky barriers of Ti, Mo, Co, Ni, Pd, and Au on (100) β-Ga2O3 substrates were analyzed using a combination of current-voltage (J-V), capacitance-voltage (C-V), and current-voltage-temperature (J-V-T) measurements. Near-ideal, average ideality factors for Ti, Mo, Co, and Ni were 1.05–1.15, whereas higher ideality factors (∼1.3) were observed for Pd and Au contacts. Barrier heights ranging from 0.60 to 1.20 eV were calculated from J-V measurements for the metals with low ideality factors. C-V measurements of all Schottky metals were conducted and yielded average barrier heights ranging from 0.78 to 1.98 eV. J-V-T measurements of Ti and Co diodes yielded barrier heights of 0.81 and 1.35 eV, respectively. The results reveal a strong positive correlation between the calculated Schottky barrier heights and the metal work functions: the index of interface behavior, S = 0.70, 0.97, and 0.81 for J-V, C-V, and J-V-T data, respectively. [ABSTRACT FROM AUTHOR]

Nanocrystalline tin sulfide (SnS) thin films were deposited by electron-beam evaporation at growth temperatures ranging from room temperature to 300 °C and characterized prior to and after annealing at 300 °C in high vacuum. X-ray diffraction and Raman spectroscopy results indicated that SnS films deposited at 100 and 200 °C contained predominately a mixture of orthorhombic α-SnS and cubic π-SnS phases, whereas only α-SnS was detected in SnS films deposited at 300 °C. Contacts with a range of work functions were deposited onto p-type α-SnS films. All of the contacts investigated (Ti/Au, Ru/Au, Ni/Au, and Au) were ohmic as-deposited and yielded average specific contact resistance values that decreased with increasing metal work function, suggesting that the barrier height has at least a partial dependence on the work functions of the metals. Annealing at 350 °C for 5 min in Ar reduced the specific contact resistance value for Ru/Au contacts, resulting in the lowest value (1.9 × 10−3 Ω cm2) of contacts investigated to SnS thin films. [ABSTRACT FROM AUTHOR]

Calculated frequency distributions of atom probe tomography reconstructions (~80nm field of view) of very thin AlxGa1- xN (0.18=x=0.51) films grown via metalorganic vapor phase epitaxy on both (0001) GaN/AlN/SiC and (0001) GaN/sapphire heterostructures revealed homogeneous concentrations of Al and chemically abrupt AlxGa1- xN/GaN interfaces. The results of scanning transmission electron microscopy and selected area diffraction corroborated these results and revealed that neither superlattice ordering nor phase separation was present at nanometer length scales. [ABSTRACT FROM AUTHOR]

Nanostructured carbon (ns-C) films fabricated by stabilization and pyrolysis of diblock copolymers are of interest for a variety of electrical/electronic applications due to their chemical inertness, high-temperature insensitivity, very high surface area, and tunable electrical resistivity over a wide range [Kulkarni et al., Synth. Met. 159, 177 (2009)]. Because of their high porosity and associated high specific surface area, controlled surface cleaning studies are important for fabricating electronic devices from these films. In this study, quantification of surface composition and surface cleaning studies on ns-C films synthesized by carbonization of diblock copolymers of polyacrylonitrile-b-poly(n-butyl acrylate) at two different temperatures were carried out. X-ray photoelectron spectroscopy was used for elemental analysis and to determine the efficacy of various surface cleaning methods for ns-C films and to examine the polymer residues in the films. The in-situ surface cleaning methods included HF vapor treatment, vacuum annealing, and exposure to UV-ozone. Quantitative analysis of high-resolution XPS scans showed 11 at. % nitrogen was present in the films pyrolyzed at 600 °C, suggesting incomplete denitrogenation of the copolymer films. The nitrogen atomic concentration decreased significantly for films pyrolyzed at 900 °C confirming extensive denitrogenation at that temperature. Furthermore, quantitative analysis of nitrogen subpeaks indicated higher loss of nitrogen atoms residing at the edge of graphitic clusters relative to that of nitrogen atoms within the graphitic clusters, suggesting higher graphitization with increasing pyrolysis temperature. Of the surface cleaning methods investigated, in-situ annealing of the films at 300 °C for 40 min was found to be the most efficacious in removing adventitious carbon and oxygen impurities from the surface. [ABSTRACT FROM AUTHOR]