Evidence for Exchange Between Free and Deep Hydrogen (Deuterium) During Diffusion

1995 ◽  
Vol 377 ◽  
Author(s):  
Howard M. Branz ◽  
Sally Asher ◽  
Yueqin Xu ◽  
Mathieu Kemp
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Emission Rate ◽  
Exchange Process ◽  
Interior Layer ◽  
Exchange Processes ◽  
Hydrogen Deuterium ◽  
The Mean ◽  
Hydrogenated Amorphous ◽  
Secondary Ion ◽  
Tracer Experiments

ABSTRACTWe do not observe any immobile deuterium in secondary ion mass spectrometry D profiles taken after long anneals of hydrogenated amorphous silicon sandwich structures with a thin deuterated interior layer. This suggests that a single deep H level (∼1.4 eV deep) controls H diffusion. On its face, our result contradicts nuclear magnetic resonance and H effusion measurements that show about 30% of H in a-Si:H is “isolated” and deeply bound (∼ 2.1 eV deep). We reconcile our experimental results with the existence of isolated deep H by assuming there is a low-barrier (<< 1.4 eV) exchange process between free H and deep D. In tracer experiments, exchange has the effect of increasing the apparent emission rate of the deep D to nearly that of the shallowest trapped H. We solve for the D profiles and confirm that a deep-trapped D component is consistent with our D tracer profiles if and only if exchange processes are important. We also find that the mean distance D travels before retrapping (100–200Å) is determined by an exchange process of free D with trapped H.

Secondary ion mass spectrometry study of photorefractive-damage-resistant locally Er/Mg-doped near-stoichiometric Ti:Mg:Er:LiNbO3 strip waveguides

2010 ◽  
Vol 25 (9) ◽  
pp. 1822-1832 ◽  
Author(s):  
De-Long Zhang ◽  
Ping-Rang Hua ◽  
Li Qi ◽  
Bei Chen ◽  
Edwin Yue-Bun Pun
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Gaussian Function ◽  
Waveguide Layer ◽  
Lateral Direction ◽  
Er Doping ◽  
Depth Direction ◽  
Ion Mass Spectrometry ◽  
The Mean ◽  
Secondary Ion

Secondary-ion mass spectrometry (SIMS) was used to study the profile characteristics and diffusion properties of Mg, Ti, and Er ions in photorefractive-damage-resistant locally Er/Mg-diffused near-stoichiometric (NS) Ti:Mg:Er:LiNbO3 strip waveguides fabricated on two Z-cut initially congruent, undoped LiNbO3 substrates in sequence by local Er doping at 1100 °C or 1130 °C in air, Mg/Ti pre-diffusion at 1100 °C in wet O2, and post Li-rich vapor transport equilibration (VTE) treatment at 1100 °C. For comparison, a SIMS study was also carried out on the waveguides fabricated without the post-VTE treatment. In order to compensate for the refractive index decrease arising from both the Mg doping and the post-VTE treatment, and hence to get a positive net index increment profile in the Ti-diffused layer, a thicker Ti-film of around 170 nm was coated. Nevertheless, SIMS results show that the Ti diffusion reservoir, as well as the Er and Mg reservoirs, was exhausted. From the SIMS profiles, characteristic diffusion parameters such as the 1/e diffusion width (for Ti only) and depth, diffusivity, and surface concentration of the Mg, Ti, and Er ions are obtained. It is interesting that the Mg distribution in the NS waveguide layer is desirably homogeneous with a concentration [(1.7–2.0) ± 0.3 mol%] higher than the optical damage concentration threshold. The Ti profile follows a sum of two error functions along the lateral direction of NS waveguides with a diffusion width of (12–13) ± 0.5 μm, and a Gaussian function in the depth direction with a 1/e depth of (5.1–6.0) ± 0.2 μm. The Er profile follows also a Gaussian function with a 1/e depth of (3.7–4.4) ± 0.3 μm. In the NS waveguide layer, the mean diffusivity is (7.1 ± 2.2) to (8.3 ± 2.8) μm2/h for Mg, (3.5 ± 0.3) to (4.5 ± 0.4) μm2/h in the lateral direction and (0.54 ± 0.04) to (1.13 ± 0.08) μm2/h in the depth direction for Ti, and (4.1 ± 0.4) to (5.5 ± 0.5) × 10−2 μm2/h for Er. The effects of Li outward diffusion in the initial Er doping procedure, and the Mg codiffusion and post-VTE treatment on the mean Mg, Ti, and Er diffusivities are discussed in comparison with the previously reported results on single Mg, Ti, or Er diffusion and Mg/Ti codiffusion in a pure or homogeneously MgO-doped congruent LiNbO3 crystal. Finally, the keys to the success of the fabrication procedure adopted are discussed.

Deuterium Diffusion, Trapping and Stability in Buried Silicon Dioxide Layers

1998 ◽  
Vol 513 ◽  
Author(s):  
A. Boutry-Forveille ◽  
A. Nazarov ◽  
D. Ballutaud
Keyword(s):  
Mass Spectrometry ◽  
Silicon Dioxide ◽  
Isothermal Annealing ◽  
Secondary Ion Mass Spectrometry ◽  
Oxide Layers ◽  
Buried Oxide ◽  
Different Temperatures ◽  
Hydrogen Deuterium ◽  
Secondary Ion ◽  
Diffusion Profiles

ABSTRACTThe interaction of hydrogen (deuterium used as tracer) with Si-Si02-Si buried oxide layers (BOX) prepared by thermal oxidation or by oxygen implantation (SIMOX) are investigated using Secondary Ion Mass Spectrometry (SIMS) measurements combined with effusion experiments. The sample deuteration is performed at different temperatures between 150 and 300°C using a radiofrequency plasma. In SIMOX samples, the deuterium diffusion profiles analysed by SIMS show deuterium trapping on implantation defects, and deuterium diffusion in the silicon substrate by permeation through the oxide layer for temperatures higher than 250°C. The deuterium is still detected in the buried oxide layers after isothermal annealing at 600°C during 2 hours. The deuterium trapping at the siliconsilicon dioxide interfaces is analysed.

Photo-oxidation and the Absence of Photodarkening in Ge2Sb2Te5 Phase Change Material

2006 ◽  
Vol 918 ◽  
Author(s):  
Bong-Sub Lee ◽  
Ying Xiao ◽  
Stephen G. Bishop ◽  
John R. Abelson ◽  
Simone Raoux ◽  
...  
Keyword(s):  
Phase Change ◽  
Secondary Ion Mass Spectrometry ◽  
Free Carrier ◽  
Carrier Generation ◽  
Photo Oxidation ◽  
Optical Irradiation ◽  
The Mean ◽  
Change Material ◽  
Secondary Ion ◽  
Change Memory

AbstractGe2Sb2Te5 is under intense investigation for phase-change memory devices, including rewriteable DVDs where optical illumination is used to switch between the glassy and crystalline states. We investigate the influence of optical irradiation on amorphous phase. Many chalcogenides display photo-oxidation, photodarkening or photo-bleaching, but little has been reported on the Ge-Sb-Te system. Using spectroscopic ellipsometry (SE) and secondary ion mass spectrometry, we determine that the samples have a strong tendency to photo-oxidize; if this is not accounted for, then the analysis of SE data appears to show photodarkening. Other authors recently reported photodarkening in nonstoichiometric GexSb20-xTe80 [Pamukchieva et al., Proc. SPIE 5581, 608 (2004); Pamukchieva et al., J. Optoelectron. Adv. Mater 7, 1277 (2005)], but our analysis suggests that the changes were also the result of photo-oxidation. The oxide has lower value of (n, k) than Ge2Sb2Te5, and can be etched by hydrofluoric acid or water. The photo-oxidation is presumably the result of free carrier generation in the Ge2Sb2Te5. Our observation of negligible photodarkening is consistent with previous works that found less photodarkening in tellurides compared with selenides or sulfides, and that an increase in the mean coordination number, here by Ge addition, further reduces the photodarkening effect.

Microstructure and Hydrogen Dynamics in a-Si1-xCx:H

1999 ◽  
Vol 557 ◽  
Author(s):  
R. Shinar ◽  
J. Shinar ◽  
D. L. Williamson ◽  
S. Mitra ◽  
H. Kavak ◽  
...  
Keyword(s):  
Electron Cyclotron Resonance ◽  
Secondary Ion Mass Spectrometry ◽  
Total Content ◽  
Relaxation Processes ◽  
Fast Diffusion ◽  
X Ray Scattering ◽  
Boron Doped ◽  
Sputter Deposited ◽  
Hydrogenated Amorphous ◽  
Secondary Ion

AbstractSmall angle x-ray scattering (SAXS), IR spectroscopy, and deuterium secondary ion mass spectrometry (DSIMS) were used to study the microstructure and hydrogen dynamics of undoped and boron-doped if-sputter-deposited (RFS) and electron cyclotron resonance (ECR)-deposited hydrogenated amorphous silicon carbides (a-Si1-xCx:H) with x ≤ 19 at.%. The SAXS measurements indicated residual columnar-like features and roughly spherical nanovoids of total content CnV ≤ 1.0 vol.%. The growth of CnV with annealing was due largely to an increase in the average nanovoid radius. It was noticeably smaller than in RFS a-Si:H films. The IR spectra demonstrated H transfer by annealing from mostly bulk-like Si-H groups to C-bonds. The H diffusion and its temperature dependence in undoped films resembled those of a-Si:H and were consistent with the SAXS and IR data. Suppression of long-range motion of most of the H atoms, consistent with increased CnV was observed in B-doped ECR films. However, a small fraction of the H atoms appeared to undergo fast diffusion, reminiscent of the fast diffusion in doped a-Si:H. The results are consistent with impeded relaxation processes of the Si network, caused by the presence of C atoms, and H trapping at C-H bonds.

Isotope Exchange in Hydrogenated Silicon-Oxynitride (SiON) for 1.55μm Optical Waveguide Applications

2000 ◽  
Vol 609 ◽  
Author(s):  
Jinju Lee ◽  
Kangguo Cheng ◽  
Joseph W. Lyding ◽  
Huub W.M. Salemink
Keyword(s):  
Isotope Exchange ◽  
Thermal Activation ◽  
Annealing Temperature ◽  
Secondary Ion Mass Spectrometry ◽  
Exchange Process ◽  
Silicon Oxynitride ◽  
Loss Reduction ◽  
Hydrogenated Silicon ◽  
Secondary Ion ◽  
Additional Loss

ABSTRACTWe report a novel way of reducing the unwanted absorption loss in silicon-oxynitride (SiON) waveguides by replacing nitrogen-hydrogen (N-H) bonds with nitrogen-deuterium (N-D) bonds in an isotope exchange process. D was introduced to SiON layers in an atmospheric D anneal after the deposition of SiON. The deuterated SiON showed a factor of 2 less absorption at 1.51 μm than before the D anneal. This is an additional loss reduction, since a typical pre-anneal in N2 reduces the loss by a factor of 10. Compared to the loss in as-deposited SiON at this wavelength, the loss after D anneal is reduced by a factor of 20. The D annealing temperature varied from 450 to 950 °C. There is a correlation between the loss reduction and the level of isotope exchange in the SiON waveguide, and also, an onset temperature for thermal activation of the isotope exchange. This mechanism is characterized carefully by secondary ion mass spectrometry (SIMS).

TEM observations of hydrogen nanobubbles in implanted amorphous silicon

1996 ◽  
Vol 54 ◽  
pp. 972-973
Author(s):  
K.M. Jones ◽  
D.L. Williamson ◽  
S. Acco ◽  
M.M. Al-Jassim
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Solubility Limit ◽  
X Rays ◽  
Structural Morphology ◽  
X Ray Scattering ◽  
Structural Probes ◽  
Hydrogenated Amorphous ◽  
Secondary Ion ◽  
Deposited Films

Over the last two decades extensive studies on the optical and electrical properties of hydrogenated amorphous Si (a-Si:H) have been reported. However, less attention was given to the structural characterization of this material partly due to the insensitivity to hydrogen of structural probes such as x-rays and electron diffraction. From a recent set of experiments, results on the solubility limit of hydrogen in a special type of a-Si:H and the characterization of hydrogen induced complexes or nanobubbles has been reported. In this study, we report TEM observations of the structural morphology ofhydrogen related defects that support these recent measurements obtained by secondary ion mass spectrometry (SIMS) and small-angle x-ray scattering (SAXS).a-Si:H thin films for solar cells and other applications are produced by a variety of methods. In each case, the deposited films are usually not homogeneous as they have been found to contain low density inhomogenities in the size range of 1-10 nm. These defects are commonly referred to as microvoids or hydrogen-rich clusters.

DEFECT METASTABILITY IN HYDROGEN PASSIVATED POLYCRYSTALLINE SILICON

1994 ◽  
Vol 08 (26) ◽  
pp. 1627-1642 ◽  
Author(s):  
N.H. NICKEL ◽  
W.B. JACKSON ◽  
N.M. JOHNSON
Keyword(s):  
Spin Density ◽  
Polycrystalline Silicon ◽  
Secondary Ion Mass Spectrometry ◽  
Dangling Bond ◽  
Fine Grain ◽  
Spin Resonance ◽  
Defect Passivation ◽  
Hydrogenated Amorphous ◽  
Kinetics Of ◽  
Secondary Ion

A comprehensive review is presented for the defect passivation and the light-induced metastability in fine grain polycrystalline silicon (poly-Si). The passivation kinetics of grain boundary defects were examined by electron spin resonance and secondary ion mass spectrometry measurements. The spin density decreases to a residual value which strongly depends on the passivation temperature and a further low-temperature anneal reduces the spin density to N S =2.2×1016 cm −3. Illumination with white light produces additional dangling bond defects which are metastable and can be removed by an anneal at moderate temperatures. The light-induced degradation decreases with repeated illumination and annealing cycles and is restored upon re-exposure to monatomic H. Our results provide the strongest evidence to date that hydrogen is responsible for the metastability in both poly-Si:H and hydrogenated amorphous silicon.

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