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We present photoemission and LEED results concerning the interaction of decomposed germane (GeH 4 *) with a monocrystalline Ge(100)2 x 1 surface. As the sticking coefficient of undecomposed germane on Ge(100) is very weak, we catalytically decompose the germane molecules with a hot tungsten filament. Germanium substrates are heated by the Joule effect in the 20-500°C temperature range and exposed to either catalytically decomposed or undecomposed germane. The crystalline quality of the deposited films is controlled by low energy electron diffraction (LEED) and angle resolved ultraviolet photoelectron spectroscopy (ARUPS). We compare our ARUPS spectra with spectra resulting from the hydrogenation of the Ge(100) surface by means of atomic hydrogen (H*). After exposure of the Ge(100) surface to GeH 4 * at room temperature (RT), the deposited Ge films are submitted to annealings up to 250°C. At RT, the deposited Ge film is amorphous with an ARUPS signature characteristic of a polygermane. After annealing at 250°C, we recover the LEED pattern of the Ge(100)2 x 1 reconstruction. No chemical shift has been evidenced by means of X-ray photoelectron spectroscopy (XPS) between the Ge 3d core level of the deposited Ge film or Ge(100) substrate.

We present photoemmision and low energy electron diffraction (LEED) results obtained on a Ge/Si/Ge (100) heterostructure grown by very low pressure chemical vapour deposition of disilane (Si 2 H 6 or germane (GeH 4 on a Ge(100) 2×1 substrate. Both gases were catalytically dissociated at a hot tungsten filament. A thin (about 20 A thick) epitaxic Si film is deposited by means of the CVD technique on an atomatically clean Ge(100) 2×1 substrate by exposing it at 300 °C to a dissociated Si 2 H 6 gas phase. The obtained Si/Ge structure is then submitted to a subsequent dissociated GeH 4 exposure at 250°C to achieve Ge deposition. Growth of the resulting Ge/Si/Ge (100) heterostructure is followed by means of X-ray photoemission spectroscopy, angle-resolved ultraviolet photoemission spectroscopy and LEED. The main and original conclusion of our study is the possibility of Ge growth from a GeH 4 gas phase on top of a thin epitaxic Si layer previously deposited on Ge (100) from an Si 2 H 6 gas phase. Such studies, performed in reproducible ultrahigh vacuum conditions on the very first steps of interface growth, should contribute to a better understanding and control of the various parameters involved in the gas source, molecular beam epitaxial growth of forthcoming Si/Ge heterostructures.

We present photoemission and LEED results concerning the thermal and catalytic decomposition of disilane Si2H6 on a monocrystalline Ge(100)2 × 1 surface. The catalytic decomposition of disilane was obtained with a hot tungsten filament. Germanium substrates were heated by the Joule effect in the 20–500°C temperature range and exposed to either catalytically decomposed or undecomposed disilane. The thicknesses of the Si deposited layers were estimated from X-ray photoelectron spectroscopy (XPS) measurements. The crystalline quality of the deposited films could be controlled by angle resolved ultraviolet photoelectron spectroscopy (ARUPS), X-ray photoelectron diffraction (XPD) and low energy electron diffraction (LEED). For a substrate temperature around 350°C, the exposures to undecomposed or catalytically decomposed disilane lead to deposition of well-ordered Si thin films. At this substrate temperature, the Si growth rate was found to be 2–3 times higher when disilane was catalytically decomposed. At substrate room temperature, while some authors claimed the adsorption of undecomposed disilane on a Ge(100)2 × 1 surface, our results seem to show that no reaction occurs between undecomposed disilane and a Ge(100)2 × 1 surface. For substrate temperature above 400°C, the decrease of the Si photoemission intensities can be explained by an indiffusion of Si into Ge.

To shed some light on the problem of hydride adsorption on semiconducting surfaces, we have performed a photoemission study to compare gases like disilane (Si 2 H 6 ) and germane (GeH 4 ) in the condensed (or physisorbed) state (−150°C) with disilane and germane in the chemisorbed state (at room temperature). These molecules were condensed on a metallic substrate to minimize the charging effect resulting from the formation of insulating films. X-ray photoemission experiments revealed a shift of about 1.2 eV towards lower binding energies of the Si2s and Ge3d core-level peaks between the condensed state and the adsorbed state. In the chemisorbed state, the energy location of those peaks is the same as in the bulk material. We conclude that Si 2 H 6 and GeH 4 molecules are already chemisorbed on the surface at room temperature. We also found that such a “physisorbed state → chemisorbed state” transition could be induced at low temperature (−150°C) by a 2 keV Ar + ion bombardment of the condensed film. These results are discussed in relation to our previously published conclusions on hydride adsorption on semiconducting surfaces.

We present photoemission results on the thermal and catalytic decomposition of disilane (Si 2 H 6 ) on a monocrystalline Ge(111)c(2×8) surface. Catalytic decomposition of disilane is obtained at a hot tungsten filament. Germanium substrates were heated by the Joule effect in the 20–600 °C temperature range and exposed to low pressure (10 −5 Torr) Si 2 H 6 doses. The thicknesses of the Si layers deposited by both methods were estimated from X-ray photoemission spectroscopy (XPS) measurements. Valence band ultraviolet photoemission spectroscopy (UPS) is used to characterize the crystalline quality of the deposited films. The growth rate of the Si film is found to be 10 times higher when obtained after catalytic decomposition rather than by thermal decomposition of disilane. For substrate temperatures above 400 °C, we observe a silicon-germanium intermixing.

This is a study of the adsorption of hydrogen at various temperatures on Ge(111)c(2 × 8) and amorphous Ge surfaces. We observe that the only phase forming on both surfaces for temperatures above room temperature is a monohydride phase. This phase desorbs completely at 150°C. For high hydrogen exposures, coadsorbed oxygen impurities build up for substrate temperatures below 150°C. The oxygen contamination desorbs completely at 225°C. This thermal evolution allows clear distinction between the monohydride phase and oxygen contamination.

L'adsorption de disilane sur Si(111) 7 x 7 dans la gamme de température 25-550 °C fait apparaître la formation des phases mono et dihydrure déjà observées avec les systèmes Si(111) : H et Si(111) : SiH4. La phase monohydrure Si-H est maximale à 350 °C et subsiste jusqu'à 550 °C. La phase dihydrure est très importante à température ambiante (TA), inexistante à partir de 250 °C et traduit la formation d'un polysilane de type (SiH 2)n. Une surface (111) de silicium, saturée en hydrogène ou disilane à 350 °C, est passivée vis-à-vis du disilane à TA. Pour obtenir la formation d'une phase dihydrure, il est nécessaire de casser la molécule de disilane ou d'hydrogène au contact d'un filament de tungstène porté à haute température. Par comparaison avec l'adsorption de disilane sur Ge(111), nous concluons, à partir de mesures XPS, qu'une partie au moins de la phase dihydrure résulte de la fixation de groupements SiH2.

We report results on the adsorption of hydrogen and disilane on Si(111) 7 × 7 and Ge(111) surfaces studied by ultraviolet and X-ray (XPS) photoemission spectroscopies. Samples were heated in the 20–500°C temperature range and exposed to low pressure (10 −5 torr) H and Si 2 H 6 doses in the 10 3 –10 5 L exposure range. Only characteristic signatures of mono- and dihydride phases are observed. Saturation of a silicon surface with Si 2 H 6 cannot be achieved at room temperature (RT) in contrast with experiments carried out in the same conditions with atomic hydrogen. Results suggest formation of a more or less amorphous polysilane. A Si(111) surface saturated at 300°C with monohydride phase cannot subsequently adsorb Si 2 H 6 at room temperature whereas further hydrogen adsorption is still possible through dihydride phase formation. Dihydride phase formation is possible by disilane cracking at a hot tungsten filament. Disilane adsorption on a Ge(111) surface induces characteristic features of mono- and dihydride phases. No silicon deposit is evidenced by XPS at room temperature. Silicon deposition on the Ge(111) surface requires disilane cracking at a hot tungsten filament. Possible mechanisms explaining the observed results are discussed.

A good Si epitaxial growth rate on Ge (111) has been achieved at substrate temperatures as low as 350 °C thanks to the use of decomposed disilane in the catalytic chemical vapor deposition (CTL‐CVD) method. For substrate temperatures in the (100–200 °C) range, an exposure of the Ge (111) wafer to decomposed disilane led to the formation of an amorphous silicon film. The growth rate of this Si layer was found to be several times higher when using decomposed disilane rather than undecomposed disilane. At substrate temperatures above 400 °C, an interdiffusion of Si into Ge occurred in both cases of disilane and decomposed disilane exposures.

Room temperature (RT) adsorption of disilane (Si2H6) on Si(111) andGe(111) surfaces has been studied using uv photoelectron spectroscopy (UPS). Si(111) and Ge(111) substrates were atomically cleaned under uhv conditions and subsequently exposed at room temperature to low pressure (10−5 torr) Si2H6 doses. For both surfaces, only characteristic features or monohydride and polyhydride phases are evidenced. For RT disilane adsorption on Si(111), UPS spectra reveal solely polyhydride phase formation whereas Si2H6 adsorption on Ge(111) induces both mono and polyhydride phases. However, for equivalent exposure doses, UPS features associated to these two phases are significantly weaker on Ge(111) than on Si(111). For RT disilane adsorption on Ge(111), X-ray photoelectron spectroscopy (XPS) reveals no presence of silicon atoms on the Ge surface, even for heavy exposure doses. The monohydride and polyhydride phases are of comparable importance with those obtained by exposing a Ge(111) surface to molecular hydrogen. We conclude that the Ge(111) surface dissociates the H2 molecule. The resulting H radicals saturate the available dangling bonds inhibiting the sticking of H2SiSiH2 radicals. We also checked that molecular hydrogen is not decomposed by the Si(111) surface. In that case, we explain the presence of an important dihydride phase without associated monohydride by the sticking of H2SiSiH2 groups.

Hepatocyte nuclear factor 1 (HNF1) is a dimeric homeoprotein expressed in hepatocytes and in a few other epithelial cells where it helps regulate the expression of a specific subset of genes. In an attempt to identify novel target genes for HNF1 and to assess the distribution of its target sites within the vertebrate genome, we performed a computer-assisted search within the available databases using a weighted matrix. Several hundred potential target sequences were identified within the GenBank and EMBL data banks. DNA binding assays demonstrated that more than 95%, of the new sites tested (52 sites among 54) bound HNF1. Surprisingly many HNF1 target sites were found in genes that are transcribed in cell types that do not contain the protein. On the other hand these sites are 2.5 to five times more frequent in hepatic genes than expected. It seems that the presence of HNF1 sites in liver-specific genes was favoured, but that no counter-selection occurred within the rest of the genome. HNF1 binding sites in liver genes are more often associated in clusters with sites for other transcription factors and the enrichment is more pronounced in promoter regions. We identified more than 100 liver specific genes that are potentially regulated by HNF1.

Photoemission techniques have been used to discern the nature of the species involved in the adsorption of germane and catalytically decomposed germane on a Si(111)7\ifmmode\times\else\texttimes\fi{}7 surface. It has been shown that the catalytic decomposition of germane induces--at very low substrate temperature (RT--300 \ifmmode^\circ\else\textdegree\fi{}C)--in the Ge adsorption process, a mechanism quite different from the undecomposed germane adsorption. In this study, GeH, ${\mathrm{GeH}}_{2}$, and ${\mathrm{GeH}}_{3}$ radicals have been experimentally identified.

We present an in situ study of low-pressure hydrogen, silane, and disilane chemisorption on Si(111) surfaces. Only characteristic signatures of mono and dihydride phases are evidenced. At room temperature sticking of ${\mathrm{SiH}}_{2}$ or (${\mathrm{SiH}}_{2}$${)}_{\mathrm{n}}$ species for ${\mathrm{SiH}}_{4}$ and ${\mathrm{Si}}_{2}$${\mathrm{H}}_{6}$, respectively, are proposed and related to the back bonds of the dimer\char21{}adatom\char21{}stacking-fault model.

5566 Background: High EGFR expression occurs in 35–70% of primary ovarian tumors and is often associated with poor prognosis. This Phase II, open-label, non-comparative multicenter study investigated the efficacy and tolerability of gefitinib (Iressa) in combination with paclitaxel (P) and carboplatin (C) for second-line treatment of patients (pts) with ovarian, tubal or peritoneal adenocarcinoma. Methods: Women (>18 years) with platinum-resistant/refractory (relapsed 6 months) disease were enrolled. Pts received gefitinib (500 mg/day), P (175 mg/m2) and C (AUC 5) every 3 weeks for 6–8 cycles, after which pts could continue to receive gefitinib. The primary endpoint was objective response rate (ORR) assessed using RECIST or Rustin criteria. Results: Sixty-eight pts (26 resistant/refractory and 42 sensitive) were enrolled (median age [range]: 57 [34–72] years; ECOG performance status 0/1/2: 41/26/1). ORR and disease control rates were 19.2% and 69.2%, respectively, for resistant/refractory; and 61.9% and 81.0%, respectively, for sensitive pts (see table ). Grade 3/4 toxicities (in =10% pts) were neutropenia (59%), diarrhea (25%), leukopenia (22%), anemia (13%), and acne (13%). Two myelodysplastic syndromes (MDS) and one acute biphenotypic leukemia were observed during treatment. Another pt developed MDS 34 months after study treatment discontinuation. Conclusions: Gefitinib (Iressa) in combination with P and C has promising activity as second-line treatment for ovarian, tubal or peritoneal adenocarcinoma and is generally well tolerated. The hemopathies are under further investigation. [Table: see text] No significant financial relationships to disclose.

2581 Background: MUC1 is a glycoprotein often over-expressed and underglycosylated in renal cell carcinoma (RCC) making it an attractive antigenic target for tumor-specific immunotherapy. TG4010 is a cancer vaccine based on a modified vaccinia virus, strain MVA, expressing both MUC1 and Interleukin 2 (MVA-MUC1-IL2). The objective of this phase II, non-randomized study was to determine the efficacy of TG4010 alone and in combination with cytokines. Methods: Thirty seven patients (pts) with progressive metastatic RCC expressing MUC1 in at least 50% of the tumour cells were treated by subcutaneous injections of TG4010, 108 pfu/inj weekly, for 6 weeks then every three weeks until progression. At progression, TG4010 was continued in combination with Interferon α2a (INF) and Interleukin 2 (IL2). Results: Treatment efficacy and toxicities were previously presented at ASCO 2005 (abstr 4653). No objective responses have been observed, however, 7 pts (19%) remained stable for more than 6 months with TG4010 alone, 3 of them more than 22 months. After progression on TG4010 alone 22 pts received TG4010 in combination with cytokines. Six pts (27%) have been stabilized more than 6 months. The median TTP were 2.6 months (95% CI, 2.4–2.9 months) for TG4010 alone and 3.5 months (95% CI, 0.2–6.7 months) for the combined treatment. There were 24 deaths, with a median OS of 19 months (95% CI, 10–27.9) for the whole population. Seven pts were treated by sorafenib after immunotherapy failure. After censoring pts at the introduction of sorafenib, the median OS was 16 months (95% CI, 6–26), with 41% of pts alive at 2-years. The most frequent adverse effects related to TG4010 were minor to moderate injection site reactions, fatigue and flu-like symptoms. Twelve out of 24 pts evaluable for MUC1 ELISpot show evidence for MUC1-specific CD8+ T cell response while 14 out of 21 evaluable for MUC1 specific T cell proliferation were responsive. Conclusions: The cancer vaccine TG4010 alone and in combination with IL2 and INF induces some disease stabilizations in pts with progressive metastatic RCC and can improve survival in a population selected for MUC1 positivity, which is a factor of poor prognosis. [Table: see text]

4653 Background: MUC1 is a glycoprotein located at the apical surface of glandular epithelial cells. In some tumors, MUC1 is often aberrantly over-expressed and hypoglycosylated, unmasking new antigenic epitopes. This makes it a potential target for tumor-specific vaccination. In renal cell carcinoma (RCC), MUC1 expression is associated with a poor prognosis. TG4010 is a cancer vaccine based on a modified vaccinia virus (MVA) expressing both MUC1 and Interleukin 2. The phase II study objective was to determine the overall response rate of TG4010 alone and in combination with cytokines in a two-step design. Methods: Patients (pts) with progressive metastatic RCC, expressing MUC1 in at least 50% of the tumour cells, received subcutaneous injections of TG4010 weekly for 6 weeks then every 3 weeks until progression, then the TG4010 was combined with Interferon alpha-2a (INF) and Interleukin 2 (IL2). Response to treatment was evaluated every 12 weeks according to the RECIST criteria. Median time to progression...

5015 Background: EGFR expression is increased in 35–70% of primary OC, and often correlates with poor prognosis. Gefitinib (Iressa, ZD1839) is an orally active EGFR-TKI (epidermal growth factor receptor tyrosine kinase inhibitor). Methods: Multicenter, open, non-comparative study in pts with platinum-resistant (relapsed 6 months) OC, with measurable disease, or non-measurable disease with rising CA125, and after only one line-therapy with cisplatin or C, and P. Pts received gefitinib (500 mg/day), P (175 mg/m2), and C (AUC=5) every 3 weeks, for 6–8 cycles. After which, pts could continue to receive gefitinib. Response was assessed by RECIST or Rustin criteria. Results: Since April 2002, 41 pts (median age: 58 yrs (range 34–71)) and an ECOG performance status (0/1/2) of 27/14/0, were enrolled. In 40 assessed pts, 7 were non-evaluable for efficacy (early withdrawal (1), toxicity (2), no target lesions (4)). The overall response rates (CR and PR) were 25% and 71% i...

Using UPS and XPS techniques, we have focused our attention on the behaviour of Si atoms which have segregated at the topmost layer of the Si-Au interface. We have demonstrated that these Si atoms, without their usual sp 3 configuration, in a metallic environment, can be very easily oxidized even at room temperature.

We report XPS results on the thermal cracking of monosilane on a polycrystalline tantalum substrate. Ta substrates were heated in the 20°C–800°C temperature range and exposed to low pressure (10−5 Torr) SiH4 doses. We followed the Ta/TaSi2 interface growth by recording the Si2p and Ta4f core level shifts. For temperatures below 600°C, results show growth of a thin (∼ 15 A) TaSi2 film followed by a thin Si overlayer. By annealing at 750°C for 2 min, this Si surface layer intermixes with bulk tantalum. For preparation at higher temperatures (600°C–800°C), grown TaSi2 films get thicker (∼ 25 A) but the Ta/TaSi2 interface is always covered by a thin silicon overlayer. The growth process of the Ta/TaSi2 interface is limited by the diffusion coefficient of Ta through the TaSi2 film which acts as a diffusion barrier.

We present results on the thermal cracking of silane on Si(111) 7× 7 surface studied by ultraviolet (UPS) and X-ray (XPS) photoemission spectroscopy. Samples were heated in the temperature range 20°C-500°C and exposed to low pressure (10 −5 Torr) SiH 4 doses in the range 10 3 -10 5 L. Only characteristic signatures of mono and dihydride phases are evidenced. Forsilane saturation at 300 °C, the Si-H peak int the same temperature. Sticking of Si-H groups might occur atop of the rest-atoms of the DAS model.

Silicon oxynitride films (SiOxNy) are prepared by reactive, electron gun evaporation of Si at nitrogen dioxide pressures ranging from 10−6 T to 5 × 10−5 T. In this way the brightness of W-filament of the electron gun probably contributes to the photodissociation of NO2 and favours the introduction of oxygen. The oxygen composition, determined by XPS analysis, may be varied nearly over the entire range between Si and SiO2 (O < x < 2), that of the nitrogen remaining limited (y < 0.4) Starting from pure a-Si, with rising NO2 pressures and oxygen content, the resistivity and the optical transmission vary gradually — as for a-SiOx samples — to insulating and transparent samples. The XPS Si2p electron energy shift and the ESR g-value shift are also well connected with the composition and the local surroundings of the Si atoms. The behaviour of thse spectra versus the composition provides arguments for a description of the structure of the SiOxNy films with a ternary random bonding model and local bondings of the kind |Si-(Si4−X−YOXNY)| (X or Y = 0, 1, 2, 3, but Y is generally less than X, X + Y ⩽ 4). On the other hand the ESR spin density remains high (1018–1019 cm−3) if care is taken in its determination, and is not related to the conduction and the sample composition for high x values, but seems to be connected with the method of preparation.

We studied the influence of low energy (1–3 keV) H+ ion bombardment on amorphized silicon wafers. Mainly monohydride phase formation is evidenced by Ultra-violet Photoemission Spectroscopy (UPS). When previously formed mono and polyhydride phases coexist, the polyhydride phase is preferentially etched by H+ bombardment.

The structure and the growth of very thin films of silicon oxide on top of atomically clean silicon surfaces have been investigated with surface techniques such as AES, ELS, LEED and XPS under UHV conditions. A transition layer was found to form at the Si-Si02 interface. The growth kinetics could be explained by a phenomenological model based on oxygen diffusion through the oxide layer under the presence of a surface electric field. Finally the Si oxidation has also been examined with XPS technique when some metallic impurities were evaporated onto the Si surface prior to oxygen exposure. An enhanced reactivity was observed and attributed to the covalent sp3 bond disruption which was provoked by metallic impurities.

Recent studies have revealed interesting properties of the dihydride phase coexisting with the monohydride phase on the hydrogenated Si surface. The absorption of atomic hydrogen on amorphized (i.e. Ar+ ion bombarded) silicon has been studied for coverages at and below one monolayer at temperatures between 300 K and 600 K using photoemission spectroscopy (UPS and XPS). In the very first stages of room temperature (RT) adsorption (< 50 L), we detected only the monohydride phase while dihydride phase formation is observed for exposures above 50 L. For T ≥ 600 K, only the monohydride phase is present at all exposures. Experimental evidence that the adsorption sites for the SiH2 states are not produced by corrosion is presented. Identical results were obtained on amorphized Si (111) and Si (100).

Recent studies have revealed interesting properties of the dihydride phase coexisting with the monohydride phase on the hydrogenated Si surface. The adsorption of atomic hydrogen on the Si(111)7×7 surface has been studied for coverages at and below one monolayer at temperatures between 300 and 600 K using photoemission spectroscopy (UPS and XPS). In the very first stages of room temperature (RT) adsorption (

During the thermal oxidation of Si(111) surfaces performed under ultra high vacuum conditions and investigated with various surface techniques such as Auger electron spectroscopy, low energy electron diffraction, ultra violet and X-ray induced photoemission spectroscopy, the Si 2p core level binding energy was measured and provided directly the band bending variation of the Si surface. A net interface charge then could be deduced. This is an elegant in situ method to have access to the electrical characteristics of the SiSiO2 interface during its formation.

The initial stages of the Cu growth on top of a 7×7 Si(111) surface were monitored with LEED, AES, UPS, and XPS techniques. Results suggest that at room temperature the Cu growth proceeds by a laminar fashion. An intermixing between Si and Cu takes place giving rise to a diffuse interface extending to several first monolayers. This fact is testified by the splitting of the Si LVV transition in AES spectra, by the deviation of the AES and XPS Cu and Si signal plot versus coverage from a perfect layer by layer growth plot, and by a strong diffuse background intensity in LEED diagram. Moreover, at this coverage range, a slight narrowing and a shift (0.7 eV±0.2 eV) of the 3d Cu peak towards higher binding energy as compared with the bulk metal are observed in valence band photoemission spectra. With increasing coverage, a metal rich phase is found displaying an ordered 1×1 Cu(111) planelike structure. No Si enrichment at the topmost metallic layer is observed by XPS. Core level spectroscopy gives similar resu...