Long Range Hydrogen Motion, Evolution, and Bonding in a-Si:H and a-Ge:H

1990 ◽  
Vol 192 ◽  
Author(s):  
R. Shinar ◽  
X.-L. Wu ◽  
S. Mitra ◽  
J. Shinar
Keyword(s):  
Structural Relaxation ◽  
Hydrogen Diffusion ◽  
Secondary Ion Mass Spectrometry ◽  
Diffusion Length ◽  
Diffusion Constant ◽  
Arrhenius Behavior ◽  
Ir Studies ◽  
Prolonged Annealing ◽  
Constant Diffusion ◽  
Secondary Ion

ABSTRACTThe results of secondary ion mass spectrometry and IR studies of hydrogen diffusion in a-Si:H and a-Ge:H are reviewed and discussed. In a-Si:H, the diffusion is significantly slower at low total H content. The exponent α of the power-law time dependent diffusion constant D(t) = Doo(ωt)−α does not decrease with temperature as 1-T/To. D(tL), for constant diffusion length L, thus deviates from an Arrhenius behavior. The “apparent” activation energy Ea and prefactor Do derived from lnD(tL) vs 1/T yield a Meyer-Neldel relation Do = Aooexp(Ea/kToo) irrespective of L, H content, or microstructure. Aoo ≅ 3.3 × 10−14cm2/s and Too ≅ 730K for 2.5 × 10−5 ≤ Do ≤ 102cm2/s and 1.3 ≤ Ea ≤ 2.2eV. The preliminary results on a-Ge:H are similar, with Aoo ≅ 1.3 × 10−15cm2/s and Too = 530K. It is suspected that deviations from an exponential distribution of H site energies, structural relaxation, and deep H trapping sites related to microvoids may all contribute to the deviation of α from a 1-T/To behavior. Measurements following prolonged annealing suggest structural relaxation that affects H-site energies.

Transportation of Na and Li in Hydrothermally Grown ZnO

2009 ◽  
Vol 1201 ◽  
Author(s):  
Pekka Tapio Neuvonen ◽  
Lasse Vines ◽  
Klaus Magnus Johansen ◽  
Anders Hallén ◽  
Bengt Gunnar Svensson ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Activation Energy ◽  
Formation Energy ◽  
Secondary Ion Mass Spectrometry ◽  
Diffusion Constant ◽  
Zinc Vacancy ◽  
Diffusion Source ◽  
Secondary Ion ◽  
Zinc Site ◽  
Limited Diffusion

AbstractSecondary ion mass spectrometry has been applied to study the transportation of Na and Li in hydrothermally grown ZnO. A dose of 1015 cm-2 of Na+ was implanted into ZnO to act as a diffusion source. A clear trap limited diffusion is observed at temperatures above 550 °C. From these profiles, an activation energy for the transport of Na of ∼1.7 eV has been extracted. The prefactor for the diffusion constant and the solid solubility of Na cannot be deduced independently from the present data but their product estimated to be ∼3 × 1016 cm-1s-1. A dissociation energy of ∼2.4 eV is extracted for the trapped Na. The measured Na and Li profiles show that Li and Na compete for the same traps and interact in a way that Li is depleted from Na-rich regions. This is attributed to a lower formation energy of Na-on-zinc-site than that for Li-on-zinc-site defects and the zinc vacancy is considered as a major trap for migrating Na and Li atoms. Consequently, the diffusivity of Li is difficult to extract accurately from the present data, but in its interstitial configuration Li is indeed highly mobile having a diffusivity in excess of 10-11 cm2s-1 at 500 °C.

IR and Sims Study of Hydrogen Diffusion in RF Sputter Deposited Boron Doped a-Si:H and Undoped a-Ge:H

1989 ◽  
Vol 149 ◽  
Author(s):  
S. Mitra ◽  
X.-L. Wu ◽  
R. Shinar ◽  
J. Shinar
Keyword(s):  
Hydrogen Diffusion ◽  
Secondary Ion Mass Spectrometry ◽  
Stretch Vibration Band ◽  
Vibration Band ◽  
Boron Doped ◽  
Multiple Trapping ◽  
Stretch Vibration ◽  
Order Of Magnitude ◽  
Sputter Deposited ◽  
Secondary Ion

ABSTRACTSecondary ion mass spectrometry (SIMS) and IR measurements of long range deuterium motion in rf sputter deposited (rf sp) p-doped a-Si:H and undoped a-Ge:H are compared to recently published results on undoped rf sp a-Si:H, which exhibited strongly power-law time dependent diffusion constants (exponent α= 0.75±0.1) in films of as-deposited content of di-H and tri-H bonds (usually associated with microvoids) Ndo –4–5 at.%. In pdoped a-Si:H samples where Ndo-l.8–3.8at.%, the diffusion is much faster, but the exponent is similar. In undoped a-Ge:H exhibiting a stretch vibration band indicative of mono-H bonding only, the diffusion is about one order of magnitude faster than in undoped a-Si:H, and α = 0.23. The results are discussed in relation to both the multiple trapping (dispersive) and defect mediated diffusion models.

Comparative Study of Hydrogen Diffusion in Hot-Wire and Glow-Discharge-Deposited a-Si:H

1999 ◽  
Vol 557 ◽  
Author(s):  
J. Shinar ◽  
R. Shinar ◽  
K. E. Junge ◽  
E. Iwaniczko ◽  
A. H. Mahan ◽  
...  
Keyword(s):  
Glow Discharge ◽  
Hydrogen Diffusion ◽  
Secondary Ion Mass Spectrometry ◽  
Error Function ◽  
Interface Layer ◽  
Hot Wire ◽  
Release Times ◽  
Multiple Trapping ◽  
Complementary Error Function ◽  
Secondary Ion

AbstractLong-range atomic H motion in hot-wire deposited (HW) a-Si:H is compared directly to that in glow-discharge deposited (GD) a-Si:H by monitoring the deuterium secondary ion mass spectrometry (DSLMS) profiles in [GD a-Si:H]/[GD a-Si:(H,D)]/[HW a-Si:H] multilayers vs annealing temperature and time. While the profiles in the GD layer are in excellent agreement with complementary error-function behavior and previous studies, the profiles in the HW layer suggest that the multiple-trapping motion of the H and D atoms is much slower, possibly due to an interface layer of defects. However, an exponential “tail” of D atoms extends deep into the HW layer, probably due to a long diffusion length of mobile D atoms, consistent with the established release times of H and D from the GD layer and H loss typical during growth of HW films. The results are also discussed in terms of the H exchange model and compared to previous NMIR studies of HW a-Si:H, which suggest that most of the hydrogen in the HW layer is concentrated in H-rich clusters dispersed in a network of very low H content.

Hydrogen Dynamics and Tee Distribution of H Sites in Undoped a-Si:H and a-Ge:H

1991 ◽  
Vol 219 ◽  
Author(s):  
R. Shinar ◽  
X.-L. Wu ◽  
S. Mitra ◽  
J. Shinar
Keyword(s):  
Mass Spectrometry ◽  
Activation Energy ◽  
Long Range ◽  
Secondary Ion Mass Spectrometry ◽  
Ir Studies ◽  
Multiple Trapping ◽  
Ion Mass Spectrometry ◽  
Secondary Ion ◽  
Trapping Sites

ABSTRACTSecondary ion mass spectrometry and IR studies of long-range hydrogen motion in undoped a-Si:H and a-Ge:H of varying H content and microstructure are reviewed and discussed. In particular, their relation to the multiple trapping (MT) model, the role of microvoids, the significance of the Meyer-Neldel relation (MNR), and the nature of H sites is addressed. It is suggested that while the MT mechanism may be significant in a-Si:H of low H content Cfj, it is largely marginal in films where CH ≥ 10 at.% H and in a-Ge:H. Mono Si-H bonds on microvoid surfaces are apparently deep H trapping sites up to ∼ 400°C, but H is desorbed from such sites in a-Ge:H above 180°C. The MNR between the diffusional activation energy and prefactor is observed among the various a-Si:H and a-Ge:H, but its significance is questionable, and may be due to the MT mechanism only in low H content a-Si:H. The nature of the distribution of H sites is also discussed.

The Effect of Temperature and Si Concentration on the Mixing of AlAs/GaAs Superlattices

1986 ◽  
Vol 77 ◽  
Author(s):  
Ping Mei ◽  
H. W. Yoon ◽  
T. Venkatesan ◽  
S. A. Schwarz ◽  
J. P. Harbison
Keyword(s):  
Activation Energy ◽  
Molecular Beam ◽  
Secondary Ion Mass Spectrometry ◽  
Diffusion Length ◽  
Dopant Concentration ◽  
Effect Of Temperature ◽  
Surface Layers ◽  
Near Surface ◽  
Depth Profiles ◽  
Secondary Ion

ABSTRACTThe intermixing of AlAs/GaAs superlattices has been investigated as a function of Si concentration following anneals in the range of 500 to 900 C. The superlattice samples were grown by molecular beam epitaxy(MBE) and the near surface layers were doped with silicon at concentrations of 2×10 to 5×1018 cm-3. Si and Al depth profiles were measured with secondary ion mass spectrometry (SIMS).The diffusion length and activation energy of Al as a function of silicon dopant concentration are derived from the SIMS data. In the temperature range studied an activation energy for the Al interdiffusion of -4eV is observed with the diffusion coefficients increasing rapidly with Si concentration.

Hydrogen Diffusion in Undoped and B-Doped a-Si1-xCx:H

1994 ◽  
Vol 336 ◽  
Author(s):  
R. Shinar ◽  
J. Shinar ◽  
G. Subramania ◽  
H. Jia ◽  
S. Sankaranarayanan ◽  
...  
Keyword(s):  
Hydrogen Diffusion ◽  
Electron Cyclotron Resonance ◽  
Secondary Ion Mass Spectrometry ◽  
Diffusion Constant ◽  
Fast Diffusion ◽  
Carrier Recombination ◽  
Boron Doped ◽  
Stretch Vibration ◽  
B Doping ◽  
Resonance Plasma

ABSTRACTA deuterium secondary ion mass spectrometry (SIMS) study of hydrogen diffusion in undoped and boron-doped a-Si0.86C0.4:H deposited by an electron cyclotron resonance plasma is described. The undoped films deposited at 250°C clearly indicated deuterium-hydrogen interdiffusion at T ≥ 350°C. The dispersion parameter a of the power-law time dependent diffusion constant D = D00(ωt)−α decreased from ∼0.3 at T = 350 and 400°C to ∼0.1 at 450°C, and the activation energy for a diffusion length of 1000 Å was ∼1.0 eV. These results are discussed in relation to previous studies of a-Si:H. The diffusion in ∼0.2 and ∼0.6 at.% B-doped a-Si0.86C0.14:H sharply differs from that in B-doped a-Si:H, where an enhancement of up to ∼103 was previously observed. In doped a-Si0.86C0.14:H, the diffusion of most of the H atoms is strongly suppressed, but a small fraction undergoes fast diffusion. IR Measurements indicate that the B-doping reduces the bulk-like Si-H stretch vibration at ∼2000 cm1. Upon annealing, the Si-CHn and C-H wag modes at ∼780 and ∼1000 cm−1, resp., increase, while the 640 and ∼2000 cm1 Si-H wag and stretch modes, resp., weaken, indicating transfer of hydrogen from Si- to C-bonds, in which the H atoms are apparently deeply trapped. As in a-Si:H, the fast diffusion component is apparently due to carrier recombination-enhanced weak Si-Si bond breaking. The results suggest that B-doping also induces microvoids and enhances the rate of breaking of weak Si-C bonds, leading to enhanced trapping of H.

A study of hydrogen diffusion in crystalline silicon by secondary-ion mass spectrometry

1989 ◽  
Vol 67 (4) ◽  
pp. 379-383 ◽  
Author(s):  
B. Y. Tong ◽  
X. W. Wu ◽  
G. R. Yang ◽  
S. K. Wong
Keyword(s):  
Mass Spectrometry ◽  
Diffusion Coefficient ◽  
Mass Spectroscopy ◽  
Hydrogen Diffusion ◽  
Secondary Ion Mass Spectrometry ◽  
Crystalline Silicon ◽  
Nuclear Resonance ◽  
Secondary Ion Mass Spectroscopy ◽  
Flux Model ◽  
Secondary Ion

The diffusion coefficient of hydrogen in crystalline silicon, obtained from recent profiling experiments such as nuclear resonance retention and secondary-ion mass spectroscopy, is 3–9 orders of magnitude smaller than the previously accepted value measured by Van Wieringen and Warmoltz in 1956. Here we point out several items often overlooked in the analysis of profiling measurements. A limited flux model is proposed to explain the observed results. Predictions by the model are supported by further experiments.

Self-Diffusion in Covalent Amorphous Solids – A Comparative Study Using Neutron Reflectometry and SIMS

2007 ◽  
Vol 263 ◽  
pp. 51-56 ◽  
Author(s):  
Harald Schmidt ◽  
Mukul Gupta ◽  
Udo Geckle ◽  
Michael Bruns
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Diffusion Length ◽  
Diffusion Processes ◽  
Amorphous Solid ◽  
Amorphous Solids ◽  
Neutron Reflectometry ◽  
Amorphous Silicon Nitride ◽  
Self Diffusion ◽  
Secondary Ion

The self-diffusion of nitrogen is studied in amorphous silicon nitride, which is a model system for a covalently bound amorphous solid with a low atomic mobility where reliable diffusion data are still lacking. Comparative experiments on Si14Nx/Si15Nx (x ≈ 1.33) isotope multilayers were carried out with secondary ion mass spectrometry (SIMS) and neutron reflectometry (NR), respectively. It was found that experiments with SIMS are not very well suited for the determination of diffusivities in a broad temperature range. The minimum diffusion length of about 5-10 nm detectable with this method is too large. At high temperatures (> 1200 °C) the amorphous solid crystallizes before any diffusion is measured and at low temperatures (< 1100 °C) the diffusivities are too low to be detected. In contrast, with neutron reflectometry diffusion lengths in the order of 1 nm and diffusivities down to 10-24 m2 s-1 were measured between 950 and 1250 °C. The potential of this method for the determination of ultra slow diffusion processes is discussed.

Hydrogen Diffusion and Solubility in A-Si:H

1994 ◽  
Vol 336 ◽  
Author(s):  
Wolfhard Beyer ◽  
Heribert Wagner
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Concentration ◽  
Hydrogen Diffusion ◽  
Diffusion Length ◽  
Activation Energies ◽  
Free Energies ◽  
Constant Diffusion ◽  
Substrate Temperatures ◽  
Concentration Diffusion ◽  
Diffusion Of Hydrogen

ABSTRACTFor plasma-grown a-Si:H films deposited at substrate temperatures between 100 and 580°C the diffusion of hydrogen was studied by SIMS profiling of H/D interdiffusion and by hydrogen evolution. The solubility for deuterium penetration into a-Si:H is found to be limited by the hydrogen concentration. Diffusion prefactors and activation energies evaluated for a constant diffusion length follow a Meyer-Neldel rule. The diffusion free energies obtained by interdiffusion and evolution experiments agree closely up to about 400°C but disagree at higher substrate temperatures.

Aspects of high-resolution imaging with a scanning ion microprobe

1986 ◽  
Vol 44 ◽  
pp. 750-751
Author(s):  
R. Levi-Setti ◽  
J. M. Chabala ◽  
Y. L. Wang
Keyword(s):  
Metal Ion ◽  
Secondary Ion Mass Spectrometry ◽  
Chromatic Aberration ◽  
Ion Source ◽  
Ion Microprobe ◽  
Emission Pattern ◽  
Intrinsic Resolution ◽  
Resolution Imaging ◽  
20 Nm ◽  
Secondary Ion

We have shown the feasibility of 20 nm lateral resolution in both topographic and elemental imaging using probes of this size from a liquid metal ion source (LMIS) scanning ion microprobe (SIM). This performance, which approaches the intrinsic resolution limits of secondary ion mass spectrometry (SIMS), was attained by limiting the size of the beam defining aperture (5μm) to subtend a semiangle at the source of 0.16 mr. The ensuing probe current, in our chromatic-aberration limited optical system, was 1.6 pA with Ga+ or In+ sources. Although unique applications of such low current probes have been demonstrated,) the stringent alignment requirements which they imposed made their routine use impractical. For instance, the occasional tendency of the LMIS to shift its emission pattern caused severe misalignment problems.

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