Production of Highly Homogeneous Si(100) Surfaces by H2O Etching:  Surface Morphology and the Role of Strain

• Published in: Journal of the American Chemical Society Vol. 128; no. 35; pp. 11455 - 11462
• Main Authors: Faggin, Marc F, Green, Sara K, Clark, Ian T, Queeney, K. T, Hines, Melissa A
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 06-09-2006
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Water; Infrared spectrometry; Scanning tunneling microscopy; Polarization; Relaxation; Fourier transformation; Steric effect; Morphology; Chemical reactivity
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja062172n

The etching of Si(100) surfaces in ultrapure water was studied with a combination of infrared spectroscopy (FTIR) and scanning tunneling microscopy (STM). While the FTIR results show that the initially rough H/Si(100) surface becomes highly homogeneous during etching, a phenomenon generally associated with surface smoothing, STM images reveal that the homogeneity is associated with the formation of well-defined etch hillocks. After many hours of etching, the resulting H-terminated surface is composed of stripes of atomically flat Si(100) terminated by etch hillocks bounded by {111}- and {110}-oriented microfacets. Polarization analysis of the Si−H stretching modes provides strong evidence for uniform dihydride-termination of the flat regions, with the narrow (∼25 Å) width of these stripes allowing for relaxation of steric strain between neighboring dihydrides. The unusual hill-and-valley etch morphology is attributed to the effects of steric strain on the reactivity of sites on the etched surface.