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Single crystals of transition metal (TM) doped β-Ga2O3, a wide gap semiconductor system of interest for transparent conductive oxide and diluted magnetic semiconductor applications, have been studied in the dilute, non-interacting limit (≤0.06 cation %). Based on optical absorption, particle induced x-ray emission, and Rutherford backscattering measurements, Mn does not incorporate as well as Cr, and Mn degrades the crystal quality. Using superconducting quantum interference device (SQuID) magnetometry, a Brillouin type paramagnetic magnetization is observed for Mn or Cr doped crystals with an effective number of Bohr magnetons per TM ion of 5.88 ± 0.1 or 3.95 ± 0.1, respectively. A trace ferromagnetic signal is consistent with a very small concentration of secondary phases in the Mn-doped crystal. The position of the edge in x-ray absorption near edge structure (XANES) measurements suggests that the Cr takes the 3+ valence, while a mixture of Mn2+ and Mn3+ are present; based on the absence of a prominent pre-edge feature in the XANES, both TM predominantly occupy an octahedral site in β-Ga2O3. Density functional theory (DFT) results, optical absorption and SQuID data are consistent with this assignment. While the Cr-doped crystal is conductive, the Mn-doped crystal is insulating, which is consistent with the Mn2+/Mn3+ mixed valence, assuming the Fermi level is pinned mid-gap at the Mn 2+/3+ transition level, which is predicted by DFT to be 1.8 eV above the valence band maximum. [ABSTRACT FROM AUTHOR]

Thermal-induced domain wall motion of tip-inverted micro/nanodomains in near-stoichiometric LiNbO3 single crystals was investigated using piezoresponse force microscopy (PFM). The domain wall motion was observed in PFM phase and amplitude images at room temperature after the sample was subjected to a thermal process at a heating temperature higher than 100 °C. In hexagonal domains with only y walls, predetermined nucleation with layer-by-layer growth is the main mechanism for the domain wall motion. In the domains composed of both x walls and y walls, the x walls are more mobile than the y walls, and the domain wall motion starts from the random nucleation of steps along the x walls that finally grow into y walls. The domain wall motion in the near-stoichiometric LiNbO3 crystal is attributed to the energy-preferable domain wall orientation, the pyroelectric effect, and the screening charge variation caused by the thermal process. [ABSTRACT FROM AUTHOR]

Nanopolar structures and local ferroelectricity of Sr0.61Ba0.39Nb2O6 relaxor crystal across Curie temperature have been investigated using piezoresponse force microscopy (PFM). The short-range nanopolar clusters are dominated by long-range ferroelectric order at room temperature, but exhibit themselves at higher temperature through the morphology change in written ferroelectric domains and persisting piezoresponse beyond Curie point. A maximum piezoresponse is observed at 80 °C, which is attributed to the peak in the dielectric permittivity near the ferroelectric phase transition. Substantial asymmetry in PFM hysteresis emerges above Curie temperature, indicating an internal bias field that becomes notable in the absence of long-range ferroelectric order. [ABSTRACT FROM AUTHOR]

We describe the screening of large combinatorial oxide libraries for their electric transport characteristics. Complete ternary composition spreads of NiO–Mn2O3–CuO oxide alloys were deposited onto conducting Nb-doped SrTiO3 substrates using the combinatorial pulsed laser deposition technique. Resistance-temperature relations for each composition in the spread were determined using a custom-designed scanning probe. Ternary and binary electrically conducting alloys are located around Ni0.45Cu0.75Mn1.65O4 (the lowest resistance point) and CuMn2O4 compositions, respectively. The temperature sensitivities of the compositions Ni0.3Cu0.3Mn2.4O4,Cu0.84Mn2.16O4, and Cu1.35Mn1.65O4 were 5.0%/°C, 3.5%/°C, and 3.0%/°C, respectively. From this screening we propose compounds for thin-film negative temperature coefficient thermistors with standardized characteristics. [ABSTRACT FROM AUTHOR]

Presents a study which described the van der Waals epitaxy and the characterization of MoSe[sub2] thin films on SnS[sub2]. Details on the experiment; Results of the study; Conclusions.

Presents a photoelectron spectroscopy study of the interaction of copper with Al[sub2]O[sub3] and AIN model systems processed under ultrahigh vacuum conditions and compares the intrinsic electronic interactions between the two cases. Evolution of the electronic structure and bonding of copper to AIN; Indication of the binding energy shift and line shape change of the aluminum core levels.