Formation of Anomalous Defect Structure on GaSb Surface by Low Temperature Sn Ion-Implantation

Abstract

Defect formation in (100) GaSb by 60 keV Sn + ion-implantation at 150-153 K is investigated using cross-sectional TEM, SEM and EDX. An anomalous structure consisting of many cells, which looks like a honey comb, was formed on the surface implanted with 8.9×10 18 ions/m 2 . The diameter and the depth of a cell were about 50 nm and 220-250 nm respectively. The thickness of the walls partitioning the cells was about 10 nm. The upper part of the partitioning wall is amorphous and rich in Ga, while the lower part shows crystalline structure. A heavily strained region of 50 nm thickness, corresponding to the maximum depth of the projected Sn ions, was observed under the cells. This defect structure is compared with similar defects which have been observed in ion-implanted GaSb. The defect formation mechanism is discussed, and an explanation based on movement of the implantation induced point defects is proposed. It is assumed that hills and hollows are formed in the early stage of implantation. The point defects created on the hills do not contribute to the development of the defect structure, because they annihilate almost completely by the recombination of vacancy and interstitial and by the movement to the near surface sink. However, under the hollows, vacancies which escaped recombination remain, and the interstitial atoms, which are highly mobile at low temperatures, migrate far from there to aggregate under the hills. The hollows become deeper by the movement of the remaining vacancies to the surface, and the hills develop into the walls by the migration of the interstitial atoms from the surrounding hollows.

Surface Sink Effects on Void Formation in GaSb and InSb under Ion Irradiation

“…By increasing the irradiation dose, the growth of voids leads to the formation of cells at the specimen surface. The cell diameter and the wall thickness partitioning the cells were about 50 and 10 nm, respectively, and the cell depth was 250 nm when irradiated with 60 keV Sn þ to a dose of 8 Â 10 14 ions/cm 2 at 150 K. 2,3) The same or similar behaviors were observed in InSb 6) and Ge. [7][8][9][10] The authors' study on those materials has been performed mainly by crosssectional transmission electron microscopy (cross-sectional TEM) in which the bulk samples are thinned after the ion irradiation, therefore, the defect formation and structural change in the bulk materials caused by ion irradiation has been investigated in the study.…”

“…The authors have found that a fine cellular structure consisting of many cells develops on the Sn þ ion irradiated GaSb surface at a low temperature (130-150 K), [1][2][3] and verified experimentally that this behavior is due to the selforganizational movement of the point defects induced by the irradiation of energetic ions. 4,5) The voids are formed by 60 keV Sn þ irradiation of a dose less than 4 Â 10 14 ions/ cm 2 .…”

“…[7][8][9][10] The authors' study on those materials has been performed mainly by crosssectional transmission electron microscopy (cross-sectional TEM) in which the bulk samples are thinned after the ion irradiation, therefore, the defect formation and structural change in the bulk materials caused by ion irradiation has been investigated in the study. [1][2][3][4] Freely migrating defects are annihilated at permanent sinks, therefore, the defect structural evolution will be greatly affected by the presence of sinks. Kiritani et al compared the differences in the damage structures in metals using both thin foil irradiation and bulk irradiation.…”

Nano-cell fabrication on semiconductor utilizing self-organizational behavior of point defects induced by ion beam

“…The idea of the nano-fabrication performed in this article was derived from the authors' discovery that the cellular structure is formed on the ion implanted GaSb surface [1]. Generally ion implantation into semiconductors creates a damaged region on their implanted surface and further implantation changes the implanted layer into amorphous structure.…”

Temperature-Dependent Energy Thresholds for Ion-Stimulated Defect Formation in Solids

“…We chose indium as the adsorbate for the present work because indium diffuses fairly quickly on both Si and Ge and therefore offers good precision for the energy threshold measurements. The basic methodology has been described previously [13,14], except that the present experiments employed a new custom ion source capable of providing a higher flux ( 2 ) and a smaller energy spread ( 4 ). Separate experiments with retarding field optics placed in front of the surface provided precise flux and energy calibrations.…”