Formamide adsorption at 80 K on clean and chemically modified Ru(001) surfaces

As part of a continuing investigation of the chemistry of various organic functional groups on the hexagonally close-packed Ru(001) surface, we have studied recently the adsorption of formamide on clean Ru(001) (Ref. 1) and on Ru(001) with an ordered p(1X2) overlayer of oxygen adatoms (θ_0 = 0.5)

Elektronenstimulierte Desorption an Stickoxiden auf Pt(100) Flächen

Electron stimulated desorption (ESD) of NO and NO$_{2}$ adsorbed on Pt(100) surfaces has been investigated. The ESD process as well as chemical reaction of nitrogen oxides on Pt(100) have been studied in combination with AES (Auger-electron spectroscopy), LEED (low energy electron diffraction) and TPD (temperature programmed desorption). Different ESD mechanisms are found to be responsible for generating positive ions from molecular and dissociated NO on Pt(100). In case of completely dissociated NO O$^{+}$ desorption occurs at low primary electron energies (< 50 eV) due to valence-band excitations. In contrast, ions from molecularly adsorbed NO on Pt(100) are desorbed by the core-level assisted ESD process exclusively: O$^{+}$ and O$^{2+}$ desorption occurs only upon bombardment with electron energies above 565 eV and 590 eV, respectively, i.e. with energies larger than the binding energy of the O$_{ls}$ adsorbate core-level. The fact that the threshold energies are 34 eV and 60 eV above the corresponding core-level binding energy is attributed to multielectron excitations. The O$^{+}$ ESD signal of this core-level assisted ESD process is found to be proportional to NO coverage up to $\theta_{NO}$ ~ 0.8. Accordingly this ESD signal can be used quantitatively to a good approximation to detect NO on Pt(100). It is shown that due to the large differences between the threshold energies for O$^{+}$ desorption from molecular and dissociated NO ESD can be applied to discriminate between these two species. For molecularly adsorbed NO$_{2}$ on Pt(100) again only the core-level assisted ESD process is operative for ion desorption. It should be noted that only N$^{+}$ but neither O$^{+}$ nor NO$^{+}_{2}$ desorption occurs. The threshold energy of 460 eV lies 55 eV above the N$_{ls}$ adsorbate binding energy. Considering the proposed bonding geometry of NO$_{2}$ on Pt(100), the lack of O$^{+}$ emission is explained by the recapture of O$^{+}$ ions due to the attractive image force. This suggestion is confirmed by the experimental findings of the electron induced dissociation of NO$_{2}$. On the basis of the detailed knowledge of the characteristic ESD signals from NO$_{2}$(ad), NO$_{(ad)}$ and O$_{(ad)}$, the ESD technique was used to investigate the adsorption and decomposition of NO$_{2}$ on Pt(100). The two modifications of the Pt(100) surface (nonreconstructed lxI and reconstructed 5x20 phase) were found to play an important role in the adsorption and decomposition behavior of NO$_{2}$ on Pt(100). By means of ESO as well as LEEO and TPO measurements it is shown that the decomposition of molecularly adsorbed NO$_{2}$ on the reconstructed surface does not follow simple dissociation kinetics and that it is accompanied by a 5x20 $\rightarrow$ 1x1 surface phase transition. Isothermal measurements give evidence for an autocatalytic reaction which occurs only above a critical coverage; the autocatalytic reaction is strongly related to the structure transformation of the Pt(100) surface

THE INFLUENCE OF X-RAY DAMAGE ON ELECTRON-INDUCED INTERFACE DEGRADATION IN MOS CAPACITORS

The radiation response of MOS capacitors and their degradation resistance after annealing has been investigated. Compared to unexposed samples, irradiated and subsequently annealed MOS capacitors were found to be more prone to electron-induced interface degradation. The enhanced degradation correlates with the initial radiation damage and is lowest in TaSi2 silicide gates. To which extent hydrogen contamination of the oxide or mechanical strain may account for the observed results will be discussed

Hysteresis of in situ CCVD grown graphene transistors

In this paper we report on a novel method to fabricate graphene transistors directly on oxidized silicon wafers without the need to transfer graphene. By means of catalytic chemical vapor deposition (CCVD) the in situ grown monolayer graphene field-effect transistors (MoLGFETs) and bilayer graphene field-effect transistors (BiLGFETs) are realized directly on oxidized silicon substrate. In situ CCVD grown BiLGFETs possess unipolar p-type device characteristics with an extremely high onoff-current ratio up to 1 × 10 7. With this novel fabrication method hundreds of large scale in situ CCVD grown graphene FETs are realized simultaneously on one 2'' wafer in a silicon CMOS compatible process

In situ CCVD grown graphene transistors with ultra-high on-off-current ratio in silicon CMOS compatible processing

We invented a novel method to fabricate graphene transistors on oxidized silicon wafers without the need to transfer graphene layers. By means of catalytic chemical vapor deposition (CCVD) the in-situ grown monolayer graphene field-effect transistors (MoLGFETs) and bilayer graphene transistors (BiLGFETs) are realized directly on oxidized silicon substrate, whereby the number of stacked graphene layers is determined by the selected CCVD process parameters. In-situ grown MoLGFETs exhibit the expected Dirac point together with the typical low on/off-current ratios between 16 (hole conduction) and 8 (electron conduction), respectively. In contrast, our BiLGFETs possess unipolar p-type device characteristics with an extremely high on/off-current ratio up to 1E7 exceeding previously reported values by several orders of magnitude. We explain the improved device characteristics by a combination of effects, in particular graphene-substrate interactions, hydrogen doping and Schottky-barrier effects at the source/drain contacts as well. Besides the excellent device characteristics, the complete CCVD fabrication process is silicon CMOS compatible. This will allow the usage of BiLGFETs for digital applications in a hybrid silicon CMOS environment

INFLUENCE OF THE FABRICATION CONDITIONS ON THE p+-TaSi2/POLY-Si GATE QUALITY

L'effet des différentes étapes de fabrication du poly-siliciure sur la qualité resultante du dopage p+ de la grille est examiné. En particulier on étudie la diffusion de bore en correlation avec la contamination en oxigène. Le rôle de l'interface TaSi2/poly-Si et de l'atmosphere de recuit sur la redistribution du bore est montré.The effect of different polycide fabrication steps on the resulting p+ gate quality is investigated. In particular the boron diffusion is studied in correlation with the oxygen contamination. The role of the quality of the TaSi2/poly-Si interface and of the annealing atmosphere on the boron redistribution are pointed ou

Elektronenstimulierte Desorption an Stickoxiden auf Pt(100) Flaechen

TIB: RA 831 (1963) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman