Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
Collection
Years
  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single crystal Si1−xGex(011) layers with x≤0.35 have been grown on double-domain Si(011)"16×2" surfaces from Si2H6/Ge2H6 mixtures at temperatures Ts=400–950 °C. D2 temperature programmed desorption was used to show that the structure of the Si(011)"16×2" surface unit cell, more correctly written as [217 21] since the unit cell vectors are nonorthogonal, is composed of 16 adatoms and eight π-bonded dimers with a dangling bond density half that of the 1×1 surface. Si1−xGex(011) overlayers are "16×2" when x〈xc(Ts) and "2×8" with x〉xc(Ts). The value of xc decreases from (similar, equals) 0.10 at Ts=475 °C to 0.08 at 550 °C to 0.06 at 650 °C. Both the "2×8" and "16×2" Si1−xGex(011) surface reconstructions gradually and reversibly transform to 1×1 at Ts between 650 and 725 °C. Film growth kinetics exhibit three distinct regimes. At low temperatures (Ts(approximately-less-than)500 °C), the film deposition rate RSiGe decreases exponentially with 1/Ts in a surface-reaction-limited growth mode for which the rate-limiting step is hydrogen desorption from Si and Ge monohydride phases. RSiGe becomes essentially constant with Ts in the intermediate impingement-flux-limited range, Ts=500–650 °C. At Ts〉650 °C, RSiGe increases again with Ts due initially (Ts(similar, equals)650–725 °C) to an increase in the steady-state dangling bond coverage as the surface reconstruction gradually transforms to 1×1. The continued increase in RSiGe at even higher Ts is associated with strain-induced roughening. Ge/Si ratios in as-deposited films are linearly proportional to the incident Ge2H6/Si2H6 flux ratio JGe2H6/JSi2H6 and nearly independent of Ts indicating that the reactive sticking probabilities of Si2H6 and Ge2H6 have very similar temperature dependencies. RSiGe(JGe2H6/JSi2H6,Ts) in both the surface-reaction-limited and flux-limited regimes is well described by a simple kinetic model incorporating second-order dissociative chemisorption and second-order hydrogen desorption as rate-limiting steps. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fully-coherent Si0.7Ge0.3 layers were deposited on Si(001) by gas-source molecular beam epitaxy (GS-MBE) from Ge2H6/Si2H6 mixtures in order to probe the effect of steady-state hydrogen coverages θH on surface morphological evolution during the growth of compressively strained films. The layers are grown as a function of thickness t at temperatures, Ts=450–550 °C, for which strain-induced roughening is observed during solid-source MBE (SS-MBE) and deposition from hyperthermal beams. With GS-MBE, we obtain three-dimensional (3D) strain-induced growth mounds in samples deposited at Ts=550 °C for which θH is small, 0.11 monolayer (ML). However, mound formation is dramatically suppressed at 500 °C (θH=0.26 ML) and completely eliminated at 450 °C (θH=0.52 ML). We attribute these large differences in surface morphological evolution primarily to θH(Ts)-induced effects on film growth rates R, adatom diffusion rates Ds, and ascending step-crossing probabilities. GS-MBE Si0.7Ge0.3(001) growth at 450 °C remains two dimensional, with a surface width 〈w〉〈0.15 nm, at all film thicknesses t=11–80 nm, since both R and the rate of mass transport across ascending steps are low. Raising Ts to 500 °C increases R faster than Ds leading to shorter mean surface diffusion lengths and the formation of extremely shallow, rounded growth mounds for which 〈w〉 remains essentially constant at (similar, equals)0.2 nm while the in-plane coherence length 〈d〉 increases from (similar, equals)70 nm at t=14 nm to 162 nm with t=75 nm. The low ascending step crossing probability at 500 °C results in mounds that spread laterally, rather than vertically, due to preferential attachment at the mound edges. At Ts=550 °C, the ascending step crossing probability increases due to both higher thermal activation and lower hydrogen coverages. 〈w〉(t) increases by more than a factor of 10, from 0.13 nm at t=15 nm to 1.9 nm at t=105 nm, while the in-plane coherence length 〈d〉 remains constant at (similar, equals)85 nm. This leads, under the strain driving force, to the formation of self-organized 3D {105}-faceted pyramids at 550 °C which are very similar to those observed during SS-MBE. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: CrN layers, 0.5 μm thick, were grown on MgO(001) at Ts=570–775 °C by ultrahigh vacuum magnetically unbalanced magnetron sputter deposition in pure N2 discharges at 20 mTorr. Layers grown at Ts≤700 °C are stoichiometric single crystals exhibiting cube-on-cube epitaxy: (001)CrN||(001)MgO with [100]CrN||[100]MgO. At higher temperatures, N2 desorption during deposition results in understoichiometric polycrystalline films with N fractions decreasing to 0.35, 0.28, and 0.07 with Ts=730, 760, and 775 °C, respectively. The surface morphologies of epitaxial CrN(001) layers were found to depend strongly on the incident ion-to-metal flux ratio JN2+/JCr which was varied between 1.7 and 14 with the ion energy maintained constant at 12 eV. The surfaces of layers grown with JN2+/JCr=1.7 consist of self-organized square-shaped mounds, due to kinetic roughening, with edges aligned along orthogonal 〈100〉 directions. The mounds have an average peak-to-valley height 〈h〉=5.1 nm and an in-plane correlation length of 〈d〉=0.21 μm. The combination of atomic shadowing by the mounds with low adatom mobility results in the formation of nanopipes extending along the growth direction. Increasing JN2+/JCr to 14 leads, due to increased adatom mobilities, to much smoother surfaces with 〈h〉=2.5 nm and 〈d〉=0.52 μm. Correspondingly, the nanopipe density decreases from 870 to 270 μm−2 to 〈20 μm−2 as JN2+/JCr is increased from 1.7 to 6 to 10. The hardness of dense CrN(001) is 28.5±1 GPa, but decreases to 22.5±1 GPa for layers containing significant nanopipe densities. The CrN(001) elastic modulus, 405±15 GPa, room-temperature resistivity, 7.7×10−2 Ω cm, and relaxed lattice constant, 0.4162±0.0008 nm, are independent of JN2+/JCr. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Boron doping concentrations (approximately-greater-than)6×1019 cm−3 were found to increase Si(001) growth rates RSi at low temperatures while decreasing RSi at higher temperatures during gas-source molecular beam epitaxy (GS-MBE) from Si2H6 and B2H6. In order to probe the mechanisms governing these effects, Si(001) samples with B coverages θB ranging from 〈0.05 to (approximately-equal-to)0.5 ML were prepared by exposing clean Si(001)2×1 wafers to B2H6 doses between 2×1017 and 4×1020 cm−2 at 200–400 °C. The samples were then heated to 700 °C to desorb the hydrogen, cooled to 200 °C, and exposed to atomic deuterium until saturation coverage. D2 temperature programmed desorption spectra exhibit β2 and β1 peaks due to dideuteride and monodeuteride desorption at 405 and 515 °C as well as new B-induced peaks, β2* and β1*, at 330 and 470 °C. Increasing θB increases the area under β2* and β1* at the expense of β2 and β1. Moreover, the total D coverage continuously decreases from (approximately-equal-to)1.23 ML in the absence of B to (approximately-equal-to)0.74 ML at θB=0.5 ML. We propose that the observed B-induced decrease in the Si*-D bond strength, where Si* represents surface Si atoms bonded to second-layer B atoms, is due to charge transfer and increased Si* dimer strain. The Si* to B charge transfer also deactivates Si surface dangling bonds causing the decrease in θD. These results are used to explain the GS-MBE growth kinetics. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: B-doped Si(001) films, with concentrations CB up to 1.7×1022 cm−3, were grown by gas-source molecular-beam epitaxy from Si2H6 and B2H6 at Ts=500–800 °C. D2 temperature-programed desorption (TPD) spectra were then used to determine B coverages θB as a function of CB and Ts. In these measurements, as-deposited films were flash heated to desorb surface hydrogen, cooled, and exposed to atomic deuterium until saturation coverage. Strong B surface segregation was observed with surface-to-bulk B concentration ratios ranging up to 1200. TPD spectra exhibited β2 and β1 peaks associated with dideuteride and monodeuteride desorption as well as lower-temperature B-induced peaks β2* and β1*. Increasing θB increased the area under β2* and β1* at the expense of β2 and β1 and decreased the total D coverage θD. The TPD results were used to determine the B segregation enthalpy, −0.53 eV, and to explain and model the effects of high B coverages on Si(001) growth kinetics. Film deposition rates R increase by ≥50% with increasing CB〉˜1×1019 cm−3 at Ts≤550 °C, due primarily to increased H desorption rates from B-backbonded Si adatoms, and decrease by corresponding amounts at Ts≥600 °C due to decreased adsorption site densities. At Ts≥700 °C, high B coverages also induce {113} facetting. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...