Precise surface measurements at the nanoscale

• Published in: Measurement science & technology Vol. 21; no. 5; p. 054004
• Main Authors: Fedina, L I, Sheglov, D V, Kosolobov, S S, Gutakovskii, A K, Latyshev, A V
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.05.2010
• Subjects: Atomic force microscopy; Calibration; Nanocomposites; Nanomaterials; Nanostructure; Replication; Self assembly; Uncertainty
• ISSN: 0957-0233; 1361-6501
• DOI: 10.1088/0957-0233/21/5/054004

Availability of self-assembly effects occurring at the atomically clean Si(1 1 1) surface during high temperature anneals in an ultrahigh vacuum chamber for fabrication of a precise calibrator at nanoscale measurements is discussed. These effects provide formation of ordered monatomic step arrays assembled by step bunches divided by almost singular surface areas with widely spaced monatomic steps suitable for calibration of atomic force microscopes. The monatomic step height at the Si(1 1 1) surface and its replication by the native oxide layer was attested by the high-resolution transmission electron microscopy followed by Digital Micrograph analysis and found to be equal to interplanar spacing (0.314 nm) in the volume of Si crystal with plus or minus 0.001 nm of accuracy. Excellent replication of the monatomic step height by oxide film covering the Si surface makes available precise AFM calibration at the nanoscale at ambient conditions. The averaged step height measured by AFM scanning of 1 X 1 mu m2 is found to be 0.314 plus or minus 0.003 nm (~1% of uncertainty). However, when the scan area becomes bigger than 2 X 2 mu m2, the height measurement uncertainty increases sharply 15 times (0.310 plus or minus 0.034 nm). We assume that this is due to differences between piezo element calibrations at small and large scan areas. The height measurement uncertainty for step bunches with well-defined quantity of steps (28) even at a large scan area (18 X 18 mu m2) turns out to be 0.3%.