Atomic level analysis of carbon and silicon by a scanning atom probe

Carbon nanotubes, chemical vapor deposition (CVD) diamond, high-temperature-high-pressure (HPHT) diamond, vitreous carbon, graphite and silicon are analyzed by a scanning atom probe (SAP). All specimens contain a large amount of hydrogen. The CVD diamond grown in hydrogen exhibits the highest hydrogen concentration with a ratio of hydrogen to carbon atoms (H/C of 2.02, and vitreous carbon has the lowest hydrogen concentration with a H/C ratio of 0.25. Significant difference is noticed in the hydrogen desorption energy among analyzed CNTs. The [111]-oriented silicon wafers are chemically etched by HF and NH4F. Although a few analyzed areas are hydrogen-covered and stay clean even when exposed to air, most areas are contaminated with hydrogen, oxygen and carbon. The carbon concentration in the HF-treated silicon is found to be slightly higher than that in the NH4F-treated silicon. An unexpected finding is the shift of the most abundant Si-H clusters from Si4H+ to Si2H+ with the depth of the analyzed area of the NH4F-treated silicon.