James S. Solomon

Magnetron sputter deposition of A-15 and BCC crystal structure tungsten thin films

The effect of processing parameters on the crystal structure and electrical resistivity of magnetron sputter deposited tungsten thin films was investigated. Formation of body centered cubic (bcc) W was favored when the concentration of impurity oxygen atoms in the films was <5 at.% while the formation of A-15 W was favored between 6 and 10 at.% oxygen. A transition from A-15 W films to bcc W films occurred as the oxygen was removed from the deposition chamber by presputtering the target for extended periods of time. The binding energies of the W atoms in A-15 and bcc W films are similar, as is the binding energy of the O atoms in the two different crystal structures, indicating that the oxygen is not present as a tungsten oxide compound. The resistivity of A-15 W films is always higher than the resistivity of bcc W films due to the increased oxygen concentration and small grain size of the A-15 films. However, the sputter deposition pressure is found to have a greater effect on resistivity. This is attributed to the formation of cracks in the film.

Characterization of SiO using fine features of X-ray K emission spectra

Abstract The fine features of silicon and oxygen K X-ray emission spectra may be used to characterize thin film and bulk ‘SiO’. The Si Kα satellites Kα3 and Kα4, Si Kβ and Kβ′, and the OK band are all very sensitive to chemical combination. The X-ray spectral features indicate that SiO in the condensed state is an intimate mixture of Si and SiO2. The Kα3 and Kα4 satellite lines are especially valuable for quantitative analysis of the two components of SiO films.

Actinide‐activated luminescence in uranium‐implanted III‐V semiconductors

An actinide was successfully introduced into III‐V semiconductors and investigated with photoluminescence and secondary ion mass spectrometry (SIMS). The implanted uranium ion gives rise to relatively strong and sharp emissions between 1.60 to 1.69 μm in GaAs and at 1.67 μm in InP. The implantation was performed at an ion mean energy of 131 keV using a new type of high‐current metal ion source; the predicted depth profile of uranium was confirmed with SIMS. The emissions are a result of transitions between specific crystal‐field split spin‐orbit levels of possibly trivalent uranium (U3+) but most likely tetravalent uranium (U4+). The half‐width of the main 1601‐nm line in GaAs and the 1670‐nm line in InP is less than 0.46 meV at 6 K. Temperature‐dependent studies indicate that the emissions are associated with one center, and the luminescence is observed in GaAs and InP up to a temperature of 100 K after which it rapidly quenches.

Beryllium ion implantation in GaAsSb epilayers on InP

Beryllium ion implantation was used to form high acceptor concentrations in GaAs1−xSbx (0.47≤x≤0.49) epilayers on semi‐insulating InP substrates. Two implant doses were tested: Q0=5×1014 cm−2 and Q0=1×1015 cm−2 at an implant energy of E=50 keV. Electrochemical profiling and secondary‐ion‐mass spectrometry (SIMS) results confirm acceptor concentrations of NA≥1×1019 cm−3 and NA≥2×1019 cm−3 within 1000 A of the GaAs1−xSbx surface for the lower and higher implant dose, respectively. These results provide a p+ surface layer for low‐resistance ohmic contact to GaAsSb‐based devices. Optical microscopy and SIMS demonstrate rapid thermal anneal (RTA) temperature limits of T=650 °C for Q0=5×1014 cm−2 and T=600 °C for Q0=1 ×1015 cm−2. The temperature limitation is imposed by destabilization of the GaAs1−xSbx surface through Ga sputtering during implantation, and Ga and As outdiffusion during RTA.

Metalorganic chemical vapor deposition growth of GaAs:Er using Er(C 4 H 9 C 5 H 4 ) 3

Erbium doped GaAs has been grown by metalorganic chemical vapor deposition using a novel liquid precursor: Tris (n-butylcyclopentadienyl) erbium, Er(C4H9C5H4)3. Erbium doping as high as 1.2 × 1019cm−3 has been realized. The morphology was excellent at growth temperatures near 620°C. The erbium concentration was found to depend on growth temperatures due to incomplete pyrolysis of the erbium metalorganic compound. The erbium-related PL intensity was decreased when the erbium concentration exceeded ∼1.2 × 1019cm−3.

Content Mapping Techniques for Qualitative and Semiquantitative Analysis with the Electron Microbeam Probe

Content mapping of small surface areas with the electron microbeam probe can be used to quickly obtain very effectively both qualitative and quantitative information. An automatic content mapping device is available with the Hitachi Perkin-Elmer XMA-S Electron Probe Microanalyzer that can cover an area up to 50 microns by 50 microns. Compared with the conventional x-ray image, advantages of content mapping includes enhancement of the contrast of the element density distribution for specimens having an enriched element density with slight variation and for specimens under high magnification with poor contrast. The content mapping device is described and examples of content maps of various alloy composition and concentrations are shown.