Excitation-induced structural instability of semiconductor surfaces

Abstract

The present work reviews laser-induced electronic processes of structural instability on covalent semiconductor surfaces. In particular, we concentrate on the mechanism of the instability that takes place at the intrinsic sites of reconstructed surface structures. In order to elucidate the primary processes involved, we focus our attention on experimental results obtained by scanning tunnelling spectroscopy studies, to reveal surface structural changes at the atomic level, and by post-ionization spectroscopy studies, to probe desorption processes with high sensitivity. First, the results obtained for reconstructed Si surfaces and {110} surfaces of III–V compound semiconductors are systematically surveyed. The instability is characterized by local bond rupture at intrinsic surface sites that show important common features. Also, we find significantly different aspects of the instability, which depend on the basic properties of surfaces. Based on the characteristics revealed by the experimental results, we then propose a mechanistic model based on the generalized two-hole localization mechanism, and demonstrate, through the quantitative analysis of typical experimental results, that the model describes all the important features quantitatively and consistently.

Real-space investigation of fast diffusion of hydrogen on Si(001) by a combination of nanosecond laser heating and STM

“…26,27 Indeed, on the clean Si͑001͒ surface, laser excitation with comparable wavelengths and laser flux can lead to electronically induced reorganization and desorption processes. 28 However, in the latter case surface electronic states of the dangling bonds are present, which can effectively be excited by the laser light. By the adsorption of hydrogen, these electronic states are quenched.…”

Hydrogen on III-V (110) surfaces: Charge accumulation and STM signatures

“…(Indeed, very similar results have recently been obtained for adsorbed hydrogen on cerium dioxide, which looks in STM just like surface oxygen vacancies. 44 ) Here on the III-V (110) surfaces, the only case that looks significantly different is the (rarely considered experimentally [45][46][47][48][49][50][51][52][53][54][55][56][57][58] ) case of H ad − and V C under negative bias (filled states), where H ad − does not look like V C , but does look somewhat like a native (or other) adatom, Fig. 7.…”

“…59), in contrast to the standard simulated images of V A . The interpretation of these STM images was long controversial, since the experiments [45][46][47][48][49][50][51][52][53][54][55][56][57][58] show the vacancies as symmetric, but theoretical studies [59][60][61][62][63][64] always find them to be Jahn-Teller distorted. The accepted explanation 59 is that thermal flipping between two degenerate Jahn-Teller distorted structures averages out to the symmetric simulated STM image shown in the center-right in Fig.…”

“…Again, this weakening is very clear in the H ad + images. These differences are not conclusive, and the experimental images themselves do vary somewhat, [45][46][47][48][49][50][51][52][53][54][55][56][57][58] with others looking more like the simulated vacancy images, but it does seem likely that at least some of the reported images are due to H adsorption, not anion evaporation.…”

Excitation-induced germanium quantum dot formation on Si(100)-(2×1)

“…Therefore, the primary effect of the 1064 nm nanosecond laser light on the Si substrate is bulk-valence excitation to generate holes and electrons with small excess energies. 27 The energy density of the ns laser pulses used are well below the melt threshold of Si. 28 We next discuss thermal and nonthermal ͑electronic͒ effects of the excitation laser on Ge QD growth.…”