Temperature Dependence of Formation of Nanorods and Dots of Iodine Compounds on an H-Terminated Si(111) Surface in a Concentrated HI Solution

Abstract

Immersion of atomically flat, H-terminated Si(111) surfaces in 7.6 M HI for 0.5 - 4 h caused spontaneous formation of nanosized clusters at the Si surface. X-ray photoelectron spectroscopy analysis suggested that the clusters were composed of silicon iodides (such as SiHxI4-x), produced most probably by Si etching with HI. Atomic force microscopy inspection revealed that the immersion at a low temperature below about 30 degrees C led to the formation of long rod-shaped clusters, oriented in the (112) direction or equivalents, whereas the immersion at a high temperature above 30 degrees C led to the formation of circular dot clusters, their size and shape changing abruptly at about 70 degrees C. It is shown experimentally that the formation of dot clusters at a high immersion temperature is explained on the basis of thermodynamics, whereas that of oriented rod clusters at a low temperature is explained by a kinetics-controlled mechanism.

In-situ FTIR Studies on Self-Assembled Monolayers of Surfactant Molecules Adsorbed on H-Terminated Si(111) Surfaces in Aqueous Solutions

“…Formation of atomically flat, H−Si(111) surfaces by HF and NH 4 F etching was confirmed by observation of a clear step and terrace structure in air with an atomic force microscope (AFM) , and observation of a sharp strong FTIR peak at 2083.6 cm -1 , assigned to the stretching mode of Si−H bonds at the (111) terrace, in air, together with some weak peaks assigned to vibration modes of Si−H and SiH 2 bonds at steps. , Figure shows in-situ FTIR spectra in the regions of SiH x ( x = 1, 2) 26,27,29 and CH x ( x = 2, 3) vibrations for an H−Si(111) surface immersed in an aqueous solution of 1.0 × 10 -2 M SDES. The spectrum denoted as “0 min” was measured just after immersion (or just after the surfactant solution was flowed), whereas those denoted as “60 min” and “240 min” were obtained 60 and 240 min after the start of the immersion, respectively.…”

Si(111) Surface Modified with α,β-Unsaturated Carboxyl Groups Studied by MIR-FTIR

“…Incidentally, only one CO peak was observed when the adjacent bond was saturated . The peaks at 2071.1 and 2083.7 cm −1 are assigned to Si−H at the step site and Si−H at the terrace site, respectively − (those are abbreviated as “Si−H”). The twin peaks at 2128.7 and 2140.2 cm −1 which are observed only in spectrum (b) are assigned to the stretching vibration of the CC bonds of propiolic acid methyl ester .…”

“…The multiple internal reflection (MIR) method was adopted to obtain high sensitivity. The infrared beam was focused at normal incidence on an edge (45°-bevel) of the Si prism so that it was expected by calculation that the light is reflected internally about 100 times in the Si prism. − Chemically oxidized Si wafers, used as the spectral reference, were prepared by immersing in a boiling mixture of 30% H 2 O 2 and 98% H 2 SO 4 (1:1 in volume) for 5 min. Both the sample and reference compartments were purged with nitrogen gas or dry air.…”

Crystal-Face Dependence and Photoetching-Induced Increases of Dye-Sensitized Photocurrents at Single-Crystal Rutile TiO2Surfaces

“…Some examples of spontaneous ordering of metal and semiconductor , nanoparticles and formation of domain structures in self-assembled monolayers were reported. We have also been studying the formation of nanosized ordered structures, such as aligned nanoholes and nanorods, − ordered arrays of nanodots, , and ordered step structures , on single-crystal semiconductor and metal surfaces, with the aim of exploring new effective techniques for the production of ordered nanostructures.…”