Roles of defects induced by hydrogen and oxygen on the structural phase transition ofSi(111)4×1-In

Abstract

The influences of surface defects created by hydrogen and oxygen adsorption on the ͑4 ϫ 1͒ → ͑8 ϫ 2͒ structural phase transition in an In/Si͑111͒ system have been studied using low-energy electron diffraction. The transition temperature ͑T c ͒ decreased with the hydrogen exposure as compared to the clean surface, whereas it increased with the oxygen exposure. The H-induced decrease in the T c is expected and explainable by the general destructive role of defects as random disorders in the transition. In contrast, the O-induced increase of the T c is rather unusual. Mobile defects or doping effects may account for the assisting role of the O-induced defects in the condensation of the ͑8 ϫ 2͒ low-temperature phase.

Interwire coupling forIn(4×1)/Si(111) probed by surface transport

“…In this study, we restrict ourselves to the adsorption of oxygen, which chemisorbs dissociatively at room temperature on In/Si(111) [13], in agreement with theory [14]. Interestingly, oxygen increases T c , while many other adsorbates show the opposite behavior [15,16]. Moreover, it was shown that single oxygen defects also induce a structural phase transition in the adjacent defect-free In chain [17].…”

Initial stages of oxygen adsorption onIn/Si(111)-4×1

“…Global characteristics such as the transition temperature (T c ) and transport property of this In/Si(111)-4×1 surface have been reported to be affected significantly by small amounts of defects [13,[20][21][22][23][24][25][26][27][28]. In a recent series of diffraction experiments, the defects created by depositing metal atoms (In and Na) or by exposing the surface to gases (hydrogen and oxygen) were found to change the transition temperature [23][24][25]27].…”

“…In a recent series of diffraction experiments, the defects created by depositing metal atoms (In and Na) or by exposing the surface to gases (hydrogen and oxygen) were found to change the transition temperature [23][24][25]27]. Of particular interest was the adsorption of oxygen, which increased the T c of the phase transition of the In/Si(111)-4×1 surface, whereas the other defects reduced it.…”

“…Of particular interest was the adsorption of oxygen, which increased the T c of the phase transition of the In/Si(111)-4×1 surface, whereas the other defects reduced it. The effect of oxygen defects increasing T c is unique and extraordinary [24]. * glee@inha.ac.kr † hanchul@sookmyung.ac.kr Two possibilities have been suggested to explain the O-induced increase in T c ; hole doping or a correlated arrangement of the O-induced defects.…”

Tuning the conductivity along atomic chains by selective chemisorption

“…In case of Si(111)-In, e.g., the critical temperature T C for the metal insulator transition can be shifted to lower temperatures by adsorption of various atoms, which commonly destabilize the low-temperature phase. On the contrary, molecular oxygen atoms enhance cooperatively the interwire and intrawire coupling and lead to a stabilization of the insulating (8 × 2) configuration, which * tegenkamp@fkp.uni-hannover.de increases T C [12][13][14][15]. Moreover, on the Si(111)-Au (5 × 2) Si adatoms are intrinsically present and even mandatory for the formation of the geometry with the lowest (free) energy [16,17].…”