Phase transition of In/Si(111)-4×1 surface studied with low-energy electron diffraction

Abstract

The structural phase transition of an In/Si(111) surface was examined by low-energy electron diffraction (LEED). The transition temperature between the room-temperature 4×1 structure and low-temperature 8×2 structure was determined from the changes in the LEED intensity of the half-order (×2), eighth-order (8×), and fourth-order (4×) spots with temperature. The transition temperatures determined independently from three sets of LEED beam spots were within 1 K. The differently prepared In/Si(111)−4×1 surfaces, which had similar LEED quality at room temperature, showed variations of the transition temperature. The differences in the measured transition temperatures were attributed to the effects of the additional In adatoms remaining on the surface during the formation of a 4×1 reconstruction. The In adatoms suppress the condensation of the (8×2) phase, decreasing the phase transition temperature and rounding the otherwise sharp transition.

Homogeneous and heterogeneous nucleations in the surface phase transition: Si(111)4 × 1-In

“…This observation agrees well with a previous study reporting the hysteresis in the 4 × 1-to-8 × 2 transition and thus proving that the transition was first-order [27]. Figure 1(b) further shows that similar hysteresis is also observable for the 4× spots as the intensity is changed conversely to the superstructure diffraction [28]. The structural phase transition between the 4 × 1 and the 8 × 2 phases was reported to be influenced significantly by impurities at the surface [29][30][31][32][33].…”

Variation of the 4 × 1 to 8 × 2 structural transition temperature of quasi-one-dimensional indium chains upon carrier doping from Si(111) substrates

“…On the n-type substrates possessing low carrier concentrations (n1 and n2), T c was approximately 125 K, which is consistent with the values reported in previous studies (120-135 K) [1][2][3][4][5][6]. In contrast, T c decreased to 115 K on the n3 and n4 substrates with intermediate carrier concentrations.…”

“…The deduced values of T c are indicated by the dashed lines in figure 2. No significant difference in the T c values was observed between the '8×' spots and '×2' stripes for each substrate, as reported previously [2,11].…”

“…This Si(111)4 × 1-In structure exhibits quasione-dimensional metallic band dispersion along the chains at room temperature [7][8][9][10][11]. The metallic Si(111)4 × 1-In structure changes to the insulating Si(111)8 × 2-In structure at temperatures below 125 K [1][2][3][4][5][6]. This transition was identified as a first-order phase transition [12] with a thermal hysteresis of 8 K [3,4].…”

“…A single monolayer (ML) of indium (In) atoms forms an array of one-dimensional In chains with 4 × 1 periodicity on Si(111) surfaces [1][2][3][4][5][6]. This Si(111)4 × 1-In structure exhibits quasione-dimensional metallic band dispersion along the chains at room temperature [7][8][9][10][11].…”