Combined wet and dry cleaning of SiGe(001)

Abstract

Combined wet and dry cleaning via hydrofluoric acid (HF) and atomic hydrogen on Si 0.6 Ge 0.4 (001) surface was studied at the atomic level using ultrahigh vacuum scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and x-ray photoelectron spectroscopy to understand the chemical transformations of the surface. Aqueous HF removes native oxide, but residual carbon and oxygen are still observed on Si 0.6 Ge 0.4 (001) due to hydrocarbon contamination from post HF exposure to ambient. The oxygen contamination can be eliminated by shielding the sample from ambient via covering the sample in the HF cleaning solution until the sample is introduced to the vacuum chamber or by transferring the sample in an inert environment; however, both processes still leave carbon contaminant. Dry in-situ atomic hydrogen cleaning above 330 C removes the carbon contamination on the surface consistent with a thermally activated atomic hydrogen reaction with surface hydrocarbon. A postdeposition anneal at 550 C induces formation of an atomically flat and ordered SiGe surface observed by STM. STS verifies that the wet and dry cleaned surface has an unpinned Fermi level with no states between the conduction and valence band edge comparable to sputter cleaned SiGe surfaces. V

Surface electronic structure of Si1−x Ge x (001)-2 × 1: a synchrotron radiation photoemission study

“…The processes used have limited ability to produce an impurity-free SiGe surface because carbon contaminants remain. 19) Acid pre-treatments followed by annealing in an ultra-high vacuum (UHV) chamber are beneficial for establishing longrange 2 × 1 surface order on Si(001) without residual native oxides. 20,21) However, the acid processes affect Ge(001) and (In)GaAs because the intrinsic surface morphologies are lost.…”

Synthesis, Properties, and Derivatization of Poly(dihydrogermane): A Germanium-Based Polyethylene Analogue

“…This observation is consistent with the Zintl phase concept that is routinely applied to the understanding of bonding within CaGe. , The XP spectrum of as prepared (GeH 2 ) n obtained from Method 2 shows an intense emission at 29.82 eV (Figure c­(iii)); as expected, this is marginally higher than the binding energy of Ge in germanium metal because of the presence of electronegative hydrogen termination. We also observe evidence of trace surface oxidation (i.e., Ge–O (31.1 eV) and Ge–O 2 (32.5 eV)) that results from sample preparation and manipulation . All oxygen-based features are removed upon exposure to an Ar plasma, and the Ge emission attributed to (GeH 2 ) n appears at a BE of 30.06 eV.…”

“…We also observe evidence of trace surface oxidation (i.e., Ge−O (31.1 eV) and Ge−O 2 (32.5 eV)) that results from sample preparation and manipulation. 43 All oxygen-based features are removed upon exposure to an Ar plasma, and the Ge emission attributed to (GeH 2 ) n appears at a BE of 30.06 eV. In addition, while Ca emissions were not detected in the survey spectrum because they overlap with the Ge LMM signal at about 346 eV and Ge 3d emission at about 30 eV, a residual peak centered at 27.90 eV is noted and can only be assigned to Ge(2 − ) arising from residual CaGe that was not deintercalated.…”

(Invited) Rapid In-Situ Carbon and Oxygen Cleaning of In0.53Ga0.47As(001) and Si0.5Ge0.5(110) Surfaces via a H2 RF Downstream Plasma

“…Prior to being loaded into the vacuum chamber, Si 0.5 Ge 0.5 (110) samples underwent a degrease cleaning procedure and wet chemical etch, which consisted of a 10 minute sonication in acetone, a 10 minute sonication in isopropyl alcohol, a 5 minute sonication in HPLC water, followed by a dip into 2% HF/H 2 O. To minimize air exposure, the sample was pulled from the HF solution through a protective layer of toluene and placed into a beaker of toluene (5). The sample was then loaded into the vacuum system as quick as possible with an exposure to air of less than one minute to prevent reformation of the surface native oxide layer.…”