W. Dale Compton

Optical Absorption Properties of Vanadate Glasses

The optical absorption of vanadate glasses based on the system V2O5–P2O5 was measured in the range 20 cm−1 to 25 000 cm−1 at room and liquid‐nitrogen temperatures. The samples were blown films of thickness about 1–2 μ and of composition 70.0, 80.0, and 87.5 mole % V2O5. Vibrational absorption peaks were observed at about 360, 420, 680, 1010, and 1100 cm−1 with additional structure likely at about 900 cm−1 in the 70.0 mole% V2O5 films. Peaks were observed at about 330, 435, 635, 810, 1007, and 1085 cm−1 in the 87.5 mole % films. Absorption tails were observed extending from the lowest‐energy peaks to 20 and 33 cm−1 in the 70.0 and 87.5 mole % V2O5 samples, respectively. No noticeable temperature effects on spectra shape and peak positions were observed. Absorption peaks were also observed at 1038 and 1277 cm−1 in crystalline V2O5 at room temperature and at 915, 1040, and 1274 cm−1 and possibly at 1256 cm−1 at liquid‐nitrogen temperature. The peaks at about 1010 cm−1 in the glasses are thought to be the V–O...

F-Aggregate Centers in Alkali Halide Crystals

Publisher Summary The development of the field of color centers in alkali halide crystals, spanning the last sixty to seventy years, has unfolded along what appears to be a continuously lengthening and broadening avenue. As the quantity of different centers has increased to a current total of some thirty in number there has been a simultaneous advancement in the detailed understanding of individual centers and their relationships to one another. A perusal of the reviews of color-center phenomena that have appeared over the years makes it quite obvious that the F center has been the focal point of color-center research. The reasons are partly historical and partly the design of nature. Not only does the F center give rise to the most prominent optical absorption band in a large number of the alkali halides, but the simplicity of the F center (a single electron trapped by a negative ion vacancy) offers a particularly attractive defect to study from an experimental as well as a theoretical point of view. The family of centers giving rise to optical absorption bands on the long-wavelength side of the F band has received far less attention than the F center. These centers, M, R, and N, are termed F-aggregate or F-associate centers because they bear a strong genetic relationship to the F center, and like the F center they are defects which have trapped electrons. This chapter also discusses special varieties of the F-aggregate centers such as the singly ionized M center, as well as the so-called “prime” centers, which are the result of adding an electron to the normal M , R , and N centers.

Temperature, stress, and annealing effects on the luminescence from electron-irradiated silicon

Low‐temperature photoluminescence spectra are presented for Si crystals which have been irradiated with high‐energy electrons. Studies of isochronal annealing, stress effects, and the temperature dependences of the luminescence are used to discuss the nature of the luminescent transitions and the properties of defects. Two dominant bands present after room‐temperature anneal of irradiated material are discussed, and correlations of the properties of these bands are made with known Si defects. A band between 0.8 and 1.0 eV has properties which are related to those of the divacancy, and a band between 0.6 and 0.8 eV has properties related to those of the Si‐G 15 (K) center. Additional peaks appear in the luminescence after high‐temperature anneal; the influence of impurities and the effects of annealing on these lines are discussed.

Recombination luminescence from electron-irradiated Li-diffused Si

Lithium doping has a dramatic effect on the low‐temperature photoluminescence of electron‐irradiated Si. In oxygen‐lean Si with Li doping, a new irradiation‐dependent luminescence band between 0.75 and 1.05 eV is observed, which is dominated by a zero‐phonon peak at 1.045 eV. This band is believed to be due to radiative transitions involving a Li‐modified divacancy. This band is present also in oxygen‐rich, Li‐diffused Si and is accompanied by bands previously related to the si‐G 15 (K) center and the divacancy. The intensities of the Li‐modified divacancy and Si‐G 15 (K) center bands are relatively weak in the oxygen‐rich material, apparently due to the formation of lithium‐oxygen complexes which reduce the concentration of unassociated interstitial Li and O.

CURRENT OSCILLATIONS IN Si p‐i‐n DEVICES AFTER IRRADIATION WITH ONE‐MeV ELECTRONS

Current oscillations similar to those previously reported in various semiconductors with impurity‐induced traps have been observed in Si irradiated at 0°C with 1‐MeV electrons. The oscillations are altered by annealing of the devices at temperatures below 0°C.

LUMINESCENCE FROM IMPURITIES AND RADIATION DEFECTS IN CdSe AND CdS.

CdSe and CdS platelets annealed in NaCl atmosphere show strong emission attributed to donor‐acceptor pair recombination with chlorine as a substitutional donor and sodium as a substitutional acceptor. Upon irradiation with fast neutrons, CdSe : NaCl platelets exhibit a new emission band centered at about 7050 A. Chlorine‐doped CdSe platelets show a weak emission band at the same wavelengths, whose strength increases upon irradiation with neutrons. It is suggested that this new emission also arises from donor‐acceptor pair recombination with the donor being a substitutional chlorine and the acceptor a cadmium vacancy associated with a substitutional chlorine.

ELECTRON LOCAL‐MODE PHONON INTERACTION IN METAL‐INSULATOR‐SEMICONDUCTOR TUNNEL JUNCTIONS

Interactions between tunneling electrons and a variety of phonons have been previously reported in MIS tunnel junctions including zone boundary phonons, the k = 0 longitudinal optical phonon, and the B local‐mode phonon. We report here the observation of interactions between the tunneling electron and the local‐mode phonon associated with N in n‐type SiC and P, O, and perhaps C and C–O in n‐type Si. The data in SiC suggest that the interaction with the tunneling electrons arise from N substituted for Si atoms. The identification of the local modes in Si is based on agreement with infrared absorption measurements, by observation of at least two local‐mode peaks for each impurity, and a correlation between the strength of the interaction and the concentration of P and O impurities present in various crystals.

A Practical Evaporator Fixture for Vacuum Cleavage of Semiconductor Crystals

Vacuum cleavage device for producing small area evaporated metal semiconductor contacts free from oxygen or other contamination

Annealing of fast neutron damage in impurity- conducting n-type germanium.

An annealing study of neutron‐irradiated germanium containing 2.2×1017 cm−3 antimony is described. The samples originally exhibit a temperature‐independent resistivity below 10°K, corresponding to an impurity conduction band distinct from the conduction band of the germanium. Irradiation introduces a small activation energy e2 in the resistivity below 10°K. The activation energy e2 and the 78°K carrier concentration change anneal together at about 300°C. The annealing results are compared with those obtained on more pure germanium irradiated with x rays.