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The direct reaction of trimethylaluminum (TMA) on a Ge(100) surface and the effects of monolayer H2O pre-dosing were investigated using ultrahigh vacuum techniques, such as scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and x-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). At room temperature (RT), a saturation TMA dose produced 0.8 monolayers (ML) of semi-ordered species on a Ge(100) surface due to the dissociative chemisorption of TMA. STS confirmed the chemisorption of TMA passivated the bandgap states due to dangling bonds. By annealing the TMA-dosed Ge surface, the STM observed coverage of TMA sites decreased to 0.4 ML at 250 °C, and to 0.15 ML at 450 °C. XPS analysis showed that only carbon content was reduced during annealing, while the Al coverage was maintained at 0.15 ML, consistent with the desorption of methyl (-CH3) groups from the TMA adsorbates. Conversely, saturation TMA dosing at RT on the monolayer H2O pre-dosed Ge(100) surface followed by annealing at 200 °C formed a layer of Ge-O-Al bonds with an Al coverage a factor of two greater than the TMA only dosed Ge(100), consistent with Ge-OH activation of TMA chemisorption and Ge-H blocking of CH3 chemisorption. The DFT shows that the reaction of TMA has lower activation energy and is more exothermic on Ge-OH than Ge-H sites. It is proposed that the H2O pre-dosing enhances the concentration of adsorbed Al and forms thermally stable Ge-O-Al bonds along the Ge dimer row which could serve as a nearly ideal atomic layer deposition nucleation layer on Ge(100) surface. [ABSTRACT FROM AUTHOR]

The atomic layer deposition (ALD) of Gd2O3 from tris(isopropyl-cyclopentadienyl) gadolinium (Gd(iPrCp)3) and O3 is studied as a function of the O2/N2 ratio used to generate O3. ALD using O3 with low N2 content leads to the formation of a hydroxyl-terminated surface after combustion reactions during O3 exposure followed by proton transfer and ligand release during the Gd(iPrCp)3 half cycle. This condition leads to the presence of parasitic chemical vapor deposition (CVD) due to the hygroscopicity of Gd2O3. By contrast, long O3 pulses with high N2 content lead to the dehydroxylation of the surface and to the suppression of both the proton transfer during the Gd(iPrCp)3 half cycle as well as the parasitic CVD reactions. [ABSTRACT FROM AUTHOR]

Epitaxial Si-O superlattices consist of alternating periods of crystalline Si layers and atomic layers of oxygen (O) with interesting electronic and optical properties. To understand the fundamentals of Si epitaxy on O atomic layers, we investigate the O surface species that can allow epitaxial Si chemical vapor deposition using silane. The surface reaction of ozone on H-terminated Si(100) is used for the O deposition. The oxygen content is controlled precisely at and near the atomic layer level and has a critical impact on the subsequent Si deposition. There exists only a small window of O-contents, i.e. 0.7–0.9 atomic layers, for which the epitaxial deposition of Si can be realized. At these low O-contents, the O atoms are incorporated in the Si-Si dimers or back bonds (-OSiH), with the surface Si atoms mainly in the 1+ oxidation state, as indicated by infrared spectroscopy. This surface enables epitaxial seeding of Si. For O-contents higher than one atomic layer, the additional O atoms are incorporated in the Si-Si back bonds as well as in the Si-H bonds, where hydroxyl groups (-Si-OH) are created. In this case, the Si deposition thereon becomes completely amorphous. [ABSTRACT FROM AUTHOR]

The process characteristics, the surface chemistry, and the resulting film properties of Ru deposited by atomic layer deposition from (ethylbenzyl)(1-ethyl-1,4-cyclohexadienyl)Ru(0) (EBECHRu) and O2 are discussed. The surface chemistry was characterized by both combustion reactions as well as EBECHRu surface reactions by ligand release. The process behavior on TiN starting surfaces at 325 °C was strongly influenced by Ti(O,N)x segregation on the growing Ru surface with consequences for both the growth per cycle as well as the film properties. For optimized process conditions, the films showed high purity with low C and O concentrations of the order of 1020 at./cm3. Higher deposition temperature led to strong (001) fiber texture of the films on SiO2 starting surfaces. Annealing in forming gas improved the crystallinity and led to resistivity values as low as 11 μΩcm for Ru films with a thickness of 10 nm. [ABSTRACT FROM AUTHOR]

The surface chemistryand the interface formation during the initialstages of the atomic layer deposition (ALD) of Al2O3from trimethylaluminum (TMA) and H2O on InP(100)were studied by synchrotron radiation photoemission spectroscopy andscanning tunneling microscopy. The effect of the ex situ surface cleaningby either H2SO4or (NH4)2S was examined. It is shown that the native oxide on the InP surfaceconsisted mainly of indium hydrogen phosphates with a P enrichmentat the interface with InP. After a (NH4)2S treatment,S was present on the surface as a sulfide in both surface and subsurfacesites. Exposure to TMA led to the formation of a thin AlPO4layer, irrespective of the surface cleaning. The surface Fermi levelof p-type InP was found to be pinned close to midgap after H2SO4cleaning and moved only slightly further toward theconduction band edge upon TMA exposure, indicating that the AlPO4/InP interface was rather defective. (NH4)2S passivation led to a Fermi level position of p-type InPclose to the conduction band edge. Hence, the InP surface was weaklyinverted, which can be attributed to surface doping by S donors. TMAexposure was found to remove surface S, which was accompanied by ashift of the Fermi level to midgap, consistent with the removal of(part of) the S donors in combination with a defective AlPO4/InP interface. Further TMA/H2O ALD did not lead to anydetectable changes of the AlPO4/InP interface and suggestedsimple overgrowth with Al2O3. [ABSTRACT FROM AUTHOR]