The Effect Of Surface Oxides On Cu/Ta Interfacial Interactions

1999 ◽  
Vol 564 ◽  
Author(s):  
L. Chen ◽  
B. Ekstrom ◽  
J. Kelber
Keyword(s):  
Induction Period ◽  
High Vacuum ◽  
Temperature Programmed Desorption ◽  
Ultra High Vacuum ◽  
Sublimation Temperature ◽  
Surface Oxides ◽  
Oxygen Coverage ◽  
Temperature Programmed ◽  
Kinetics Of ◽  
Effect Of Surface

AbstractWe report results of Auger electron spectroscopy (AES) and temperature programmed desorption (TPD) studies under ultra high vacuum (UHV) conditions which demonstrate that even submonolayer coverages of oxygen on Ta significantly degrade the strength of Cu/Ta chemical interactions, and affect the kinetics of Cu diffusion into bulk Ta. On clean Ta, monolayer coverages of Cu will de-wet only above 600 K. A partial monolayer of adsorbed oxygen (3L O2 at 300 K) results in a reduction of the de-wetting temperature to 500 K, while saturation oxygen coverage (10 L O2, 300 K) results in de-wetting at 400 K. Diffusion of Cu into the Ta substrate at 1100 K occurs only after a 300-second induction period at this temperature. The induction period increases to 600 sec for partially oxidized Ta and to 1200 sec for saturation oxygen coverage. TPD studies indicate no desorption of Cu for temperatures below 1300 K. The higher desorption temperature of Cu (compared to the 1150 K sublimation temperature) indicates that all the Cu originally deposited is now chemically bound to Ta.

Deposition of Iron on Si(111)-(7×7): Photo- and Electron-Assisted Decomposition of Fe(CO)5

1986 ◽  
Vol 75 ◽  
Author(s):  
J. R. Swanson ◽  
C. M. Friend ◽  
Y. J. Chabal
Keyword(s):  
Auger Electron ◽  
Silicon Crystal ◽  
High Vacuum ◽  
Low Frequency ◽  
Temperature Programmed Desorption ◽  
Thermal Reaction ◽  
Ultra High Vacuum ◽  
Temperature Programmed ◽  
Ultraviolet Photons ◽  
Induced Decomposition

AbstractLaser- and electron-assisted deposition of Fe on Si(111)-(7×7) surfaces using decomposition of Fe(CO)5 has been investigated with multiple internal reflection Fourier transform infrared, Auger electron and temperature programmed desorption spectroscopies and low energy electron diffraction under ultra-high vacuum conditions. No thermal reaction was apparent in temperature programmed desorption experiments: only molecular Fe(CO)5 desorption was observed at temperatures of 150 and 170 K, corresponding to desorption energies in the range of 7–10 kcal./mole. Fe(CO)5 decomposition could be induced using either incident 1.6 keV electrons or ultraviolet photons. Significant amounts of carbon were deposited from the electron induced decomposition, consistent with earlier reports on the Si(100) surface. In contrast, ultraviolet photolysis did not result in any detectable incorporation of carbon or oxygen into the iron deposits. No partially decarbonylated Fe(CO)x, x<5, fragments were detected subsequent to exposure to photons using infrared spectroscopy. However, a new, unresolved low frequency shoulder did appear in the infrared spectrum after exposing the Fe(CO)5 covered Si(111)-(7×7) crystal to the electron beam. Iron photodeposition was evident in the Auger electron spectra obtained subsequent to photolysis and annealing of the surface to either 300 K or 1000 K in order to desorb unreacted Fe(CO)5. These data suggest that there are no surface stable Fe(CO)x, x<5, species in the photodeposition process. Instead, photolysis yields Fe atoms directly, even at low temperatures. Annealing to temperatures on the order of 1000 K subsequent to iron deposition resulted in a significant decrease in the Fe:Si ratio as measured by Auger electron spectroscopy. In addition, CO could not be readsorbed on a surface where the Fe(CO)5 had been decomposed. This is attributed to dissolution of Fe into the bulk silicon crystal.

Oxidation Kinetics of Silicon Surfaces: Reactive Sticking Coefficient, Apparent Saturation Coverage and Effect of Surface Hydrogen

1988 ◽  
Vol 131 ◽  
Author(s):  
S. M. George ◽  
P. Gupta ◽  
C. H. Mak ◽  
P. A. Coon
Keyword(s):  
Surface Temperature ◽  
Silicon Surfaces ◽  
Sticking Coefficient ◽  
Initial Oxidation ◽  
Surface Hydrogen ◽  
Oxygen Coverage ◽  
Saturation Coverage ◽  
Temperature Programmed ◽  
Kinetics Of ◽  
Effect Of Surface

ABSTRACTThe kinetics of the initial oxidation of silicon surfaces by O2 were studied using laser-induced thermal desorption (LITD), temperature programmed desorption (TPD) and Fourier Transform Infrared (FTIR) spectroscopy. The LITD results showed that the oxidation of Si(111)7×7 by O2 was characterized by two kinetic processes: an initial rapid oxygen uptake followed by a slower growth that asymptotically approached an apparent saturation oxygen coverage. The initial reactive sticking coefficient of O2 on Si(111)7×7 decreased with surface temperature. In contrast, TPD experiments on Si(111)7×7 and FTIR studies on porous silicon demonstrated that the apparent saturation oxygen coverage increased as a function of surface temperature. Experiments with preadsorbed hydrogen also revealed that silicon oxidation was inhibited as a function of increasing hydrogen coverage on the Si(111)7×7 surface.

Polymerization of C-Si Films on Metal Substrates: Potential Adhesion/Diffusion Barriers for Microelectronics

1998 ◽  
Vol 511 ◽  
Author(s):  
Li Chen ◽  
J. A. Kelber
Keyword(s):  
High Vacuum ◽  
Temperature Programmed Desorption ◽  
Diffusion Barriers ◽  
Ultra High Vacuum ◽  
Polymeric Films ◽  
Vinyl Silane ◽  
Cu Substrates ◽  
Auger Spectra ◽  
Temperature Programmed ◽  
Si Films

ABSTRACTCarbon-Silicon polymeric films have been formed by electron beam bombardment (500eV) of molecularly adsorbed vinyl silane precursors under ultra-high vacuum (UHV) conditions. Temperature programmed desorption (TPD) studies show that polymerization is occurring via the vinyl groups, while Auger spectra show that the polymerized films have compositions very similar to the starting precursors; vinyltrichlorosilane (VTCS) or vinyltrimethylsilane(VTMS). VTCSderived films ˜ 100 Å thick show no reaction with Cu substrates and no diffusion of Cu until temperatures greater than 700 K, while Cu deposited on VTMS films on Al substrates show no diffusion prior to Al reaction/decomposition at 600 K. Auger and TPD studies also show that fluorocarbon precursors, such as perfluorobenzene can be incorporated into the films by e-beaminduced reactions, a first step in the controlled growth of adherent polymer films on unreactive substrates such as Cu.

The Surface Chemistry of CdTe Mocvd

1993 ◽  
Vol 334 ◽  
Author(s):  
Wen-Shryang Liu ◽  
Gregory B. Aupp
Keyword(s):  
Surface Chemistry ◽  
Large Fraction ◽  
High Vacuum ◽  
Temperature Programmed Desorption ◽  
Ultra High Vacuum ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Temperature Programmed ◽  
Surface Decomposition ◽  
Rate Limiting

AbstractTemperature programmed desorption (TPD) studies in ultra high vacuum revealed that diethyltellurium (DETe) and dimethylcadmium (DMCd) adsorb weakly on clean Si(100) and desorb upon heating without decomposing. These precursors adsorb both weakly and strongly on CdTe(111)A, with DMCd exhibiting the stronger interaction with the surface than DETe. Dimethylcadmium partially decomposes to produce Cd adatoms; a large fraction of the excess Cd atoms desorb upon heating. In contrast, DETe desorbs without decomposing, suggesting that the rate limiting step in CdTe MOCVD on CdTe(111)A is surface decomposition of the tellurium alkyl.

Nucleation and initial growth of Pd2Si crystals on Si(111)

1993 ◽  
Vol 51 ◽  
pp. 844-845
Author(s):  
Xianghong Tong ◽  
Oliver Pohland ◽  
J. Murray Gibson
Keyword(s):  
High Vacuum ◽  
Dark Field ◽  
Ultra High Vacuum ◽  
Initial Growth ◽  
Surface And Interface ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Initial Stage ◽  
Effect Of Surface

The nucleation and initial stage of Pd2Si crystals on Si(111) surface is studied in situ using an Ultra-High Vacuum (UHV) Transmission Electron Microscope (TEM). A modified JEOL 200CX TEM is used for the study. The Si(111) sample is prepared by chemical thinning and is cleaned inside the UHV chamber with base pressure of 1x10−9 τ. A Pd film of 20 Å thick is deposited on to the Si(111) sample in situ using a built-in mini evaporator. This room temperature deposited Pd film is thermally annealed subsequently to form Pd2Si crystals. Surface sensitive dark field imaging is used for the study to reveal the effect of surface and interface steps.The initial growth of the Pd2Si has three stages: nucleation, growth of the nuclei and coalescence of the nuclei. Our experiments shows that the nucleation of the Pd2Si crystal occurs randomly and almost instantaneously on the terraces upon thermal annealing or electron irradiation.

Oxidation Kinetics of Cu-Ni Alloy Observed by in situ UHV-TEM

2007 ◽  
Vol 1026 ◽  
Author(s):  
Li Sun ◽  
John E. Pearson ◽  
Judith C. Yang
Keyword(s):  
High Vacuum ◽  
Alloy Film ◽  
Ultra High Vacuum ◽  
Cross Sectional ◽  
Primary Mechanism ◽  
Transmission Electron ◽  
Ni Alloy ◽  
Cu Oxidation ◽  
Kinetics Of

AbstractThe nucleation and growth of Cu2O and NiO islands due to oxidation of Cu-24%Ni(001) films were monitored at various temperatures by in situ ultra-high vacuum (UHV) transmission electron microscopy (TEM). In remarkable contrast to our previous observations of Cu and Cu-Au oxidation, irregular-shaped polycrystalline oxide islands were observed to form with respect to the Cu-Ni alloy film, and an unusual second oxide nucleation stage was noted. Similar to Cu oxidation, the cross-sectional area growth rate of the oxide island is linear indicating oxygen surface diffusion is the primary mechanism of oxide growth.

scholarly journals Nitrile versus isonitrile adsorption at interstellar grain surfaces

2017 ◽  
Vol 608 ◽  
pp. A50 ◽  
Author(s):  
M. Bertin ◽  
M. Doronin ◽  
X. Michaut ◽  
L. Philippe ◽  
A. Markovits ◽  
...  
Keyword(s):  
Density Functional ◽  
Surface Defects ◽  
High Vacuum ◽  
Solid Support ◽  
Ultra High Vacuum ◽  
Structural Defects ◽  
Adsorption Energies ◽  
The Difference ◽  
Temperature Programmed ◽  
Open Question

Context. Almost 20% of the ~200 different species detected in the interstellar and circumstellar media present a carbon atom linked to nitrogen by a triple bond. Of these 37 molecules, 30 are nitrile R-CN compounds, the remaining 7 belonging to the isonitrile R-NC family. How these species behave in their interactions with the grain surfaces is still an open question. Aims. In a previous work, we have investigated whether the difference between nitrile and isonitrile functional groups may induce differences in the adsorption energies of the related isomers at the surfaces of interstellar grains of various nature and morphologies. This study is a follow up of this work, where we focus on the adsorption on carbonaceous aromatic surfaces. Methods. The question is addressed by means of a concerted experimental and theoretical approach of the adsorption energies of CH3CN and CH3NC on the surface of graphite (with and without surface defects). The experimental determination of the molecule and surface interaction energies is carried out using temperature-programmed desorption in an ultra-high vacuum between 70 and 160 K. Theoretically, the question is addressed using first-principle periodic density functional theory to represent the organised solid support. Results. The adsorption energy of each compound is found to be very sensitive to the structural defects of the aromatic carbonaceous surface: these defects, expected to be present in a large numbers and great diversity on a realistic surface, significantly increase the average adsorption energies to more than 50% as compared to adsorption on perfect graphene planes. The most stable isomer (CH3CN) interacts more efficiently with the carbonaceous solid support than the higher energy isomer (CH3NC), however.

Hydridization and catalysis by lanthanide films

1984 ◽  
Vol 393 (1805) ◽  
pp. 257-276 ◽  
Keyword(s):  
Activation Energy ◽  
High Vacuum ◽  
Deuterium Atom ◽  
Ultra High Vacuum ◽  
Gas Uptake ◽  
Metal Sublattice ◽  
Hydrogen Deuterium ◽  
Higher Temperature ◽  
Temperature Programmed ◽  
Interstitial Hydrogen

Hydrogen absorption to give the dihydrides MH 2+1 containing interstitial hydrogen H i has been studied for the metals Gd, Dy, Er, Yb and Lu in the form of films deposited in ultra-high vacuum on glass. Film areas were determined by Kr adsorption, and hydrogen content, in particular inter­stitial hydrogen H i , characterized by gas uptake, temperature programmed desorption, electrical conductivity and work function measurements by the diode method. The catalytic activity of the dihydride films for the H 2 + D 2 → 2HD reaction was studied at a pressure of 1.1 Torr over 175-579 K, and at 273 K over 0.19-6.2 Torr. Arrhenius plots for the rate con­stant show a low temperature low activation energy region changing over at a temperature T c to a higher temperature higher activation energy régime, with T c on average for the five metals about 50 K below the tem­perature T max at which the interstitial hydrogen H i has disappeared. The suggested mechanisms are T < T c : D 2 + H i □ s → (D 2 H i )□ s → □ s D i + HD, (1) T > T c : D 2 + H 2 + 4□ s → 2(D i □ s ) (H i □ s ) → 4□ s + 2HD, (2) where H i □ s , D i □ s , denotes a hydrogen, deuterium, atom held on a surface octahedral site in the f. c. c. metal sublattice. These mechanisms agree with the observed approximate first-order pressure dependency down to 77 K. The rate constants at both 273 K (under T c ) and 573 K (over T c ) decrease over Gd, Dy, Er, to Yb, and rise again to Lu, and this is discussed in terms of the metal-hydrogen, H i □ s or D i □ s bond strength.

Adsorption of Silicon Tetrachloride on Si(111) 7×7

1988 ◽  
Vol 131 ◽  
Author(s):  
P. Gupta ◽  
P. A. Coon ◽  
B. G. Koehler ◽  
S. M. George
Keyword(s):  
Surface Temperature ◽  
Thermal Desorption ◽  
Temperature Programmed Desorption ◽  
Silicon Tetrachloride ◽  
Sticking Coefficient ◽  
Adsorption Model ◽  
Temperature Programmed ◽  
Kinetics Of

ABSTRACTThe kinetics of SiCl4 adsorption on Si(lll) 7×7 were studied using laser induced thermal desorption (LITD) and temperature programmed desorption (TPD) techniques. The initial reactive sticking coefficient of SiCl4 on Si(lll) 7×7 was observed to decrease with increasing surface temperature. This decrease was consistent with a precursor-mediated adsorption model. Both LITD and TPD experiments monitored SiCl2 as the main desorption product. These results suggest that SiC12 may be the stable chlorine species on the Si(lll) 7×7 surface.

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