J. S. Morgan

Characterization of rf‐sputtered InN films and AlN/InN bilayers on (0001) sapphire by the x‐ray precession method

Thin films of InN and AlN/InN bilayers have been deposited on (0001) sapphire at a variety of substrate temperatures by reactive rf‐magnetron sputtering. For all films, the c axis of the metal nitride film parallels the c axis of the sapphire substrate, and the transmission x‐ray precession method has been employed to study the nature and azimuthal coherence of the in‐plane heteroepitaxy. For the InN films, a mixture of textured and epitaxial grains persists up to ∼200 °C and solely epitaxial grains are observed at higher substrate temperatures, to a maximum adherence temperature of 525 °C. In contrast, the AlN/InN bilayers are epitaxial at substrate temperatures of 50 °C and above, and a uniform deposition can be retained up to 650 °C. These fundamental differences in adhesion, structure and morphology of the InN films and the AlN/InN bilayers on (0001) sapphire are also clearly reflected, for example, in the variation in electrical mobility with substrate deposition temperature.

Magnetic ordering and superconducting in Fe‐doped 1‐2‐3 compounds

We have doped Fe into the ground YBa2Cu3O7 and have discovered that the Fe goes primarily into one of the two Cu sites. At least 95% of the Fe substitutes into the Cu(1) site in the Cu‐O layers between Ba layers. A high valence state of iron, Fe4+, is found to exist inside this compound. For even small amounts of Fe we see a spin‐glass type of magnetic ordering of the Fe spins which we feel is associated with a tendency for antiferromagnetic couplings of the Cu(1) ions. We conclude that the Cu(2)‐O2 plane is more important than the Cu(1)‐O chain for the superconductivity in the 1‐2‐3 compounds.

Thin films of rf-magnetron sputtered InN on mica: Crystallography, electrical transport, and morphology

Reactive rf-magnetron sputtering has been employed for the growth of thin films of InN on the (001) face of mica at a variety of substrate temperatures from 50 to 550 o C. These films have been characterized by x-ray scattering, stylus profilometry, and electrical transport measurements, and their topography has been studied by SEM and STM

Antiferromagnetic ordering in 2‐1‐4 copper oxides

We have doped a small amount of Fe (0.5%) into the 2‐1‐4 superconducting oxides La2 CuO4−y and La1.85 Sr0.15 CuO4−y . Mossbauer measurements have indicated that the Fe dopants are in a high‐spin Fe3+ state, but sharp differences have been found for samples before and after annealing in Ar, as well as with and without Sr. An antiferromagnetic transition at 292 K in the Ar‐annealed La sample has been confirmed with both Mossbauer and magnetization measurements. The relevance of antiferromagnetism to the high‐temperature superconductivity has been addressed.

Sputter Deposition of Indium Nitride on The (111) Face of Elemental and Compound Semiconductors

The structure, morphology, and transport properties of thin films of InN grown on several cubic semiconductors has been studied as a function of substrate temperature. Films were deposited using rf-magnetron sputtering onto the (111) face of GaAs, Ge, Si and ZrO 2 . In general, the film structure is such that (00.1) InN parallels the (111) plane of the cubic substrate above some deposition temperature. The in-plane structural coherence duplicates the magnitude of the calculated lattice mismatch between InN and the substrate. Electrical transport properties for growth onto (111) ZrO 2 were characterized by n-type carrier concentration and mobilities ranging up to 44 cm 2 /Vsec. A morphology-induced decrease in electrical mobility is observed for deposition temperatures above 350°C, as shown by SEM.

Local atomic structure in amorphous Fe‐P alloys

Amorphous alloys Fex P100−x have been fabricated by rf sputtering in the composition range 50≤x≤75. Only a‐Fe75 P25 is ferromagnetic at 293 K, with its Mossbauer spectrum consisting of six broad lines. This simple spectrum differs markedly from that of c‐Fe3 P. Similarly, thermogravimetric analysis yielded Tc=550 K for the amorphous phase, a value considerably lower than that of the crystalline phase (700 K). The Mossbauer spectra of the samples having x≤71 were all similar quadrupole‐split doublets. Mean isomer shifts (IS) and P(H) and P(Q) distributions were determined using Window’s method. The isomer shift is nearly independent of concentration in the range studied here, but differs significantly from those of the crystalline compounds c‐FeP, c‐Fe2 P, and c‐Fe3 P. The effective quadrupole interaction is also nearly constant for 50≤x≤71, indicating a similar local Fe environment. These results contrast sharply with c‐Fe2 P and c‐FeP, which have different crystal symmetries and whose quadrupole interact...

Electron Microscopy of InN Films

This paper describes growth morphology and structure of rfmagnetron sputtered thin films of InN, studied by plan-view transmission electron microscopy (TEM) and by scanning electron microscopy (SEM). Films deposited on TEM grids, (0001) sapphire, (111) silicon and amorphous quartz were prepared for TEM by mechanical abrasion of the substrate followed by sputter etching. At low deposition temperatures (