Photoreactions of Mo(CO)6 on Potassium Precovered Silicon Surface with UV to IR Radiation

1988 ◽  
Vol 129 ◽  
Author(s):  
Z. C. Ying ◽  
W. Ho
Keyword(s):  
Uv Radiation ◽  
Wavelength Range ◽  
Silicon Surface ◽  
High Vacuum ◽  
Dissociative Adsorption ◽  
Charge Carriers ◽  
Ultra High Vacuum ◽  
Ir Radiation ◽  
Photon Irradiation ◽  
Wide Wavelength Range

ABSTRACTThe adsorption and photoreactions of Mo(CO)6 coadsorbed with K on Si(111)7×7 at 90 K have been studied under ultra-high vacuum conditions. It is found that dissociative adsorption of Mo(CO)6 on the K preadsorbed surface occurs for coverages below a monolayer. A multilayer of physisorbed Mo(CO)6 molecules is formed on top of the monolayer. Under photon irradiation physisorbed Mo(CO)6 molecules are dissociated and CO desorption is observed. The photoreactions of Mo(CO)6 occur over a wide wavelength range from the UV to IR. In contrast, only UV radiation induces photoreactions of Mo(CO)6 on the K-free Si(111)7×7 surface. Evidently K opens a new channel for the photoreactions of Mo(CO)6 on the surface. A mechanism involving interactions between photogenerated charge carriers and the substrate-adsorbate complex is proposed.

Effects of Potassium on the Adsorption and Reactions of Nitric Oxide on Silicon Surface

1988 ◽  
Vol 131 ◽  
Author(s):  
Z. C. Ying ◽  
W. Ho
Keyword(s):  
High Vacuum ◽  
Ultra High Vacuum ◽  
Thermal Heating ◽  
Photon Irradiation ◽  
Structure Changes ◽  
Function Change ◽  
Resolution Electron ◽  
High K ◽  
Work Function Change ◽  
Electron Energy Loss

ABSTRACTThe adsorption, thermoreactions, and photoreactions of NO coadsorbed with K on Si(111)7×7 at 90 K have been studied and compared with the results obtained from the Kfree surface. The experiments were performed under ultra-high vacuum conditions using high resolution electron energy loss spectroscopy, work function change measurements, and mass spectrometry. NO adsorbs both molecularly and dissociatively on the K-free surface. Two molecular N–O stretching modes are observed at 188 and 225 meV. The concentration of these NO molecules on the surface decreases as the K exposure increases and vanishes at high K exposures. A new N–O stretching mode, attributed to adsorption of NO molecules on K clusters, is observed at 157 meV. After thermal heating or photon irradiation, the surface is covered with atomic O and N. The surface is more oxidized in the presence of K. A steady decrease in the photodesorption cross section is observed as the K exposure increases and is attributed to K-induced band structure changes.

Characteristics and Recovery of SI Surfaces Plasma Etching in CHF3 / C2F6

1992 ◽  
Vol 259 ◽  
Author(s):  
H.-H. Park ◽  
K.-H. Kwon ◽  
B.-H. Koak ◽  
S.-M. Lee ◽  
O.-J. Kwon ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Silicon Surface ◽  
Secondary Ion Mass Spectrometry ◽  
High Vacuum ◽  
Silicon Layer ◽  
Ultra High Vacuum ◽  
Rapid Thermal Anneal ◽  
Condition C ◽  
Secondary Ion

ABSTRACTThe effects of SiO2 reactive ion etching (RIE) in CHF3 / C2F6 on the surface properties of the underlying Si substrate have been studied by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) techniques. The observed two major modifications are (i) a ∼50nm thick silicon layer which contains carbon and fluorine and (ii) 2∼3nm thick residue layer composed entirely of carbon, fluorine, oxygen and hydrogen on the silicon surface. The thermal behaviors of attributed peaks for C 1s, Si 2p, O 1s and F 1s of residue film have been analyzed after in-situ resistive anneal under ultra high vacuum (UHV) condition. C-F1, C-F2 and C-F3 bonds decompose and form C-CFx (x≤3) bonds above 200°C. Above 400°C, C-CFx bonds also decompose to C-C/H bonds. For recovery of the modified silicon surface, reactive ion etched specimens have been exposed to an oxygen plasma. By XPS analysis, the effect of an O2 plasma treatment has been revealed to be completed within 20min. With an O2 plasma pre-treated, a rapid thermal anneal (RTA) treatment as low as 500°2 is found to be effective for removal of impurities in the silicon.

TEM study of chemically converted SiC thin film on nanometer curved Si surface

1993 ◽  
Vol 51 ◽  
pp. 818-819
Author(s):  
A. N. Stepanova ◽  
J. Liu ◽  
K. N. Christensen ◽  
U. T. Son ◽  
K. J. Bachmann ◽  
...  
Keyword(s):  
Thin Film ◽  
Silicon Surface ◽  
Flat Surface ◽  
Mechanical Strain ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Vacuum System ◽  
Microelectronic Devices ◽  
Vacuum Microelectronic ◽  
Field Emission Cathodes

Silicon whiskers with nanometer curvature have a variety of applications such as probes in STM and AFM, or field emission cathodes for vacuum microelectronic devices. For these and other applications it is essential to stabilize the sharply curved silicon surface during usage. Carburization of the silicon surface seems to be a very suitable solution to this problem, since SiC crystals have excellent physical properties and are chemically quite inert. There have been a number of reports of the carburization of flat surface silicon wafers by chemical reaction using both CVD and MBE methods. However, to carburize while maintaining a very sharp silicon tip is extremely difficult. It is also desirable to carburize only a very thin layer, so as to avoid excessive mechanical strain arising from the large difference (∼20%) in lattice parameters.Our carburizations were carried out in a turbo-pumped ultra-high vacuum system. The silicon specimens were oxidation sharpened and cleaned in a buffered HF solution.

Ftir Studies of Water and Ammonia Decomposition on Silicon Surfaces

1990 ◽  
Vol 204 ◽  
Author(s):  
A.C. Dillon ◽  
P. Gupta ◽  
M.B. Robinson ◽  
A.S. Bracker ◽  
S.M. George
Keyword(s):  
Silicon Surface ◽  
Silicon Oxide ◽  
High Surface ◽  
High Vacuum ◽  
High Surface Area ◽  
Ftir Spectra ◽  
Ultra High Vacuum ◽  
Silicon Surfaces ◽  
Surface Species ◽  
Surface Hydrogen

ABSTRACTFourier transform infrared (FTIR) transmission spectroscopy. was used to monitor the decomposition of H2O (D2O) and NH3(ND3) on silicon surfaces. Experiments were performed in-situ in an ultra-high vacuum (UHV) chamber using high surface area poroussilicon samples. The FTIR spectra revealed that H2O dissociates upon adsorption at 300K to form SiH and SiNH2 surface species. NH3 also issociates upon adsorption at 300 K to form SiH and SiOH2 species. Silicon samples with saturation exposures of H2O and NH3 were progressively annealed from 300 K to 860 K. The FTIR spectra of an H2O-saturated silicon surface revealed that the SiOH species decomposed to form a silicon oxide species and additional surface hydrogen between 460 K and 580 K. Likewise, the SiNH2 species decomposed between 540 K and 660 K to produce silicon nitride and additional surface hydrogen. In both cases, the Sill surface species decreased as H2 desorption from the silicon surface was observed above 700 K.

In-Situ Study of the Oxide Mediated Epitaxy of CoSi2 on Si

1999 ◽  
Vol 564 ◽  
Author(s):  
M. W. Kleinschmit ◽  
M. Yeadon ◽  
J. M. Gibson
Keyword(s):  
Silicon Surface ◽  
High Vacuum ◽  
High Energy ◽  
Ultra High Vacuum ◽  
High Energy Electron ◽  
In Situ Study ◽  
Intermediate Phases ◽  
Transmission Electron ◽  
Combined Imaging

AbstractOxide Mediated Epitaxy (OME) shows promise as a method to form good quality, thin epitaxial CoSi2 films on most Si surfaces. We have performed an in-situ study of the OME of CoSi2, on the Si (001) surface. Our work was carried out with our specially modified ultra-high vacuum transmission electron microscope (UHV TEM) SHEBA (Surface High Energy Electron Beam Apparatus). With SHEBA we were able to monitor the diffraction pattern and therefore the phase formation throughout the anneal. Our results confirm the suppression of intermediate phases during CoSi2 formation in the OME process. We also see a difference in the as deposited Co film when the oxide coated silicon surface is used rather than a clean substrate. From combined imaging and diffraction studies we will shed some light on the mechanism behind the success of OME.

Morphology and Laser-Induced Photochemistry of Silicon and Nickel Nanoparticles

2014 ◽  
Vol 605 ◽  
pp. 593-596
Author(s):  
Y.N. Parkhomenko ◽  
A.I. Belogorokhov ◽  
A.P. Bliev ◽  
V.G. Sozanov ◽  
A.G. Kaloeva ◽  
...  
Keyword(s):  
Oxide Film ◽  
Aluminum Oxide ◽  
Silicon Nanoparticles ◽  
High Vacuum ◽  
Nanocrystalline Silicon ◽  
Ultra High Vacuum ◽  
Aluminum Oxide Film ◽  
Photon Irradiation ◽  
Oxide Support ◽  
Nanosecond Pulsed Laser

The structural and photoinduced properties of silicon nanoparticles obtained by plasmachemical and electrolytic techniques and the nickel particles deposited on aluminum oxide film in ultra-high vacuum are investigated by Auger electron spectroscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy and time-of-flight spectroscopy. It is found that substantial increase of silicon nanoparticle photoinduced luminescence can be attributed to particle specific structure, as well as to the SiO2thin film which is formed on the nanocrystalline silicon surface. In case of Ni particles deposited on aluminum oxide film at low mean coverage of about 0.04 monolayers, when the film can be viewed as consisting of separated single adsorbed atoms or very small clusters, the photon irradiation by nanosecond pulsed laser leads to NO desorption. At monolayer Ni coverage formed at a substrate temperature of 80 K laser irradiation causes dissociation of NO molecules. Efficiency of this process at the initial stage is notably enhanced compared to that of NO on the bulk Ni (111) crystal. This enhancement can be attributed to the effect of underlying aluminum oxide support.

Thin Pyrolytic Graphite Films for Electron Microscope Substrates

1971 ◽  
Vol 29 ◽  
pp. 226-227 ◽  
Author(s):  
George H. N. Riddle ◽  
Benjamin M. Siegel
Keyword(s):  
Vacuum Chamber ◽  
Pyrolytic Graphite ◽  
High Vacuum ◽  
Dark Field ◽  
Ultra High Vacuum ◽  
Graphite Substrate ◽  
Nickel Substrate ◽  
Routine Procedure ◽  
Field Electron Microscopy ◽  
Dark Field Electron

A routine procedure for growing very thin graphite substrate films has been developed. The films are grown pyrolytically in an ultra-high vacuum chamber by exposing (111) epitaxial nickel films to carbon monoxide gas. The nickel serves as a catalyst for the disproportionation of CO through the reaction 2C0 → C + CO2. The nickel catalyst is prepared by evaporation onto artificial mica at 400°C and annealing for 1/2 hour at 600°C in vacuum. Exposure of the annealed nickel to 1 torr CO for 3 hours at 500°C results in the growth of very thin continuous graphite films. The graphite is stripped from its nickel substrate in acid and mounted on holey formvar support films for use as specimen substrates.The graphite films, self-supporting over formvar holes up to five microns in diameter, have been studied by bright and dark field electron microscopy, by electron diffraction, and have been shadowed to reveal their topography and thickness. The films consist of individual crystallites typically a micron across with their basal planes parallel to the surface but oriented in different, apparently random directions about the normal to the basal plane.

A High Voltage Electron Microscopy Study of Sub-Oxide Formation in Vanadium

1971 ◽  
Vol 29 ◽  
pp. 212-213
Author(s):  
R. H. Geiss ◽  
R. L. Ladd ◽  
K. R. Lawless
Keyword(s):  
High Vacuum ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Ultra High Vacuum ◽  
Pure Oxygen ◽  
Pressure Oxidation ◽  
High Voltage Electron Microscopy ◽  
Oxidation Study ◽  
Voltage Electron ◽  
Good Agreement

Detailed electron microscope and diffraction studies of the sub-oxides of vanadium have been reported by Cambini and co-workers, and an oxidation study, possibly complicated by carbon and/or nitrogen, has been published by Edington and Smallman. The results reported by these different authors are not in good agreement. For this study, high purity polycrystalline vanadium samples were electrochemically thinned in a dual jet polisher using a solution of 20% H2SO4, 80% CH3OH, and then oxidized in an ion-pumped ultra-high vacuum reactor system using spectroscopically pure oxygen. Samples were oxidized at 350°C and 100μ oxygen pressure for periods of 30,60,90 and 160 minutes. Since our primary interest is in the mechanism of the low pressure oxidation process, the oxidized samples were cooled rapidly and not homogenized. The specimens were then examined in the HVEM at voltages up to 500 kV, the higher voltages being necessary to examine thick sections for which the oxidation behavior was more characteristic of the bulk.

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