THERMAL-DESORPTION OF ULTRAVIOLET-OZONE OXIDIZED GE(001) FOR SUBSTRATE CLEANING

X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (A ES), electron energy loss spectroscopy (EELS), and reflection high-ene rgy electron diffraction (RHEED) have been used to show that 30 min ex posures of a degreased and deionized-water-rinsed Ge(001) wafer to ult raviolet (UV)-ozone in laboratory air is sufficient to remove C contam ination and form a nonpermeable passive amorphous GeO2 layer with a th ickness of congruent-to 1.8 nm. Subsequent annealing in ultrahigh vacu um (UHV) at greater-than-or-equal-to 390-degrees-C for greater-than-or -equal-to 30 min resulted in desorption of the oxide layer and the exp osure of a clean well-ordered Ge(001) 2 X 1 surface. No impurities, in cluding C and O, were detected by either XPS or AES. EELS spectra from the clean surface showed well-defined peaks corresponding to transiti ons involving dangling bonds, surface states, and surface plasmons. Sh orter UV-ozone exposures (i.e., < 30 min) often resulted in residual C contamination while incomplete oxide removal was obtained at lower ox ide desorption temperatures. Ge overlayers deposited by molecular beam epitaxy at temperatures between 200 and 450-degrees-C on UV-ozone pro cessed substrates were found by a combination of plan-view and cross-s ectional transmission electron microscopy to be highly perfect single crystals with abrupt film/substrate interfaces and no detectable dislo cations or extended defects.