A. Sagar

Effect of the Polarity of the III‐V Intermetallic Compounds on Etching

For the III‐V intermetallic compounds, the directions are polar axes. The shape of etch pits bounded by crystallographic planes and the presence or absence of pits at dislocations are influenced by the effect of the polar axes on the etch rates. Studies of these effects are reported for several etches on InSb, InAs, GaSb, and GaAs. Correlation of these studies with published x‐ray investigations shows that these etches reveal dislocations and truncated pyramidal pits only on {111} surfaces that are at the group III end of the polar axis. A difference in the shape of the pits on opposite {100} surfaces was found and is explained by means of the polar axes.

Dislocation Studies in Bi2Te3 by Etch‐Pit Technique

Dislocation studies in Bi2Te3 were made by etch‐pit technique. All work was done on c planes. The etch marks the dislocations in the c plane by producing etch grooves, and marks the sites of emergence of dislocations from the surface with pyramidal etch pits. Evidence was found for the presence of networks of dislocations lying predominantly in the c plane. Experimental evidence was also found for bending of the dislocations within the crystal being responsible for different size pyramidal etch pits, and flat bottom pits observed on the etched surfaces. The same mechanism was found to be responsible for bringing out new etch pits on longer etching. The slip traces on the c plane were found by controlled surface‐damage studies to be parallel to the binary axes.

Study of Band Structure of Intermetallic Compounds by Pressure Experiments

The effect of hydrostatic pressure on the transport properties of n‐type GaSb, InP, GaP, and p‐type PbTe was measured to study their band structure. (1) The Seebeck coefficient, Hall coefficient, and resistance of three n‐GaSb samples were measured as a function of hydrostatic pressure up to 17 000 atm between 200° and 400°K. The Seebeck coefficient α increased with pressure and approached a constant value at about 10 000 atm. The saturation value of α does not follow the simple 32 lnT relation for any of the samples; e.g., for a sample with RH(77°K) ≈95 coul−1 cm3, the saturation value of α decreases with temperature. The contribution due to the phonon‐drag effect has been considered as a possible explanation for this phenomenon. (2) The conductivity of p‐PbTe increased almost exponentially with pressure both at 300° and 194°K; the Hall coefficient at 300°K decreased by about 5% at 8000 atm, while the conductivity increased by 55% at this pressure. (3) The resistance of n‐InP samples increased with press...

Discrepancies from a Perfect Match in the Etch Patterns on the Opposite Cleavage Faces in Bi2Te3

Experimental evidence has been obtained, establishing that the deviations from a perfect one‐to‐one correspondence between etch pits on the opposite cleavage faces in Bi2Te3 are often due to bending and branching of the dislocations at the cleavage. It is suggested that the observation of deviations from the identical etch patterns on the opposite cleavage faces of a crystal does not necessarily imply the unreliability of an etch for revealing dislocations in that crystal.

Etch‐Pit Patterns and Crystal Structure of PtSb2

The lack of fourfold symmetry about the 〈100〉 axes of PtSb2 (cubic class Th) is revealed by a simple etching technique. The relative intensities of the 102 and 012 spots in a Laue back reflection pattern for a (001) surface are correlated with the etch‐pit pattern.

Investigation of Copper Diffusion in Bi2Te3 by Etching Technique

Copper diffusion in bismuth telluride crystals in the room‐temperature range was studied by etching technique. Small etch pits due to copper particles along the dislocations were observed in samples in which copper was diffused for a few hours at room temperature. Such pits were not observed along the dislocations in samples in which copper diffusion at room temperature took place for a few days. This suggests that pits observed for short diffusion times represent copper diffusion along the dislocations. No such evidence was found for copper diffusion along dislocations in the high‐temperature range.

Etches for Revealing Dislocations and Growth Striations in PtSb2

The etching of PtSb2 was investigated. It was found that the common acids would not attack this material indicating that it has a low percentage of ionic character to the bonds. An etchant to reveal dislocations and segregation striations was found. To reveal segregation striations, an impurity is necessary. The dislocations can be revealed on the three major crystallographic directions on both n‐ and p‐type material as can segregation striations.