Hydrogen diffusion in phosphorous doped polycrystalline silicon was investigated by deuterium diffusion experiments. The presence of phosphorous enhances hydrogen diffusion. For high hydrogen concentrations the activation energy of the effective diffusion-coefficient amounts to 0.25-0.35 eV. At low hydrogen concentrations diffusion is governed by deep traps that are present in an appreciable concentration of 6×108 - 1019 cm−3. The hydrogen chemical-potential, 9H, decreases with increasing temperature at a rate of ˜ 0.002 eV/K. The data are discussed in terms of a two-level model used to describe hydrogen diffusion in amorphous and undoped polycrystalline silicon.

We report on experiments which observe on a microscopic scale the migration of isolated hydrogen in InP, GaAs, and InAs. Using the radioactive acceptor 117Cd, Cd-H pairs have been formed in these III-V semiconductors. After the decay of 117Cd to 117In, H is no longer bound to an acceptor and can diffuse freely. This diffusion has been observed by perturbed yy angular correlation (PAC) spectroscopy. At 10 K, the occupation of two different lattice sites by hydrogen has been observed. First results on the diffusion of hydrogen will be discussed.

Hydrogen diffusion in CuInSe 2 single crystals and CuInS2 thin films was studied by measuring the spreading of implantation profiles upon annealing. Deep implantation with an ion energy of 10 keV and sub-surface implantation with 300 eV were applied. The diffusion coefficients in both materials were found to be in the order of 10-14 to 10-13 cm2/s in the temperature range between 400 and 520 K.These fairly low diffusivities are typical for a trap and release transport process rather than intrinsic diffusion of interstitial hydrogen. In the polycrystalline CuInS2 films, hydrogen leaves the sample through the grain boundaries.

Cold neutron prompt gamma-ray activation analysis has proven useful for nondestructive measurement of trace hydrogen. The sample is irradiated in a beam of neutrons; the presence of hydrogen is confirmed by the emission of a 2223 keV gamma-ray. Detection limits for hydrogen are 3 mg/kg in quartz and 8 mg/kg in titanium. We have used the technique to measure hydrogen in titanium alloys, germanium, quartz, fullerenes and their derivatives, and other materials.

Mass fractions of hydrogen in titanium matrices have been measured using neutron incoherent scattering (NIS) and compared with results from prompt gamma activation analysis (PGAA). Qualitatively, NIS is a more efficient technique than PGAA which involves neutron absorption, and the former may be suitable for on-line analysis. However, for NIS the scattering contribution comes from both the hydrogen and the matrix, whereas prompt gamma emission has minimal matrix effect. To isolate the signal due to hydrogen scattering, a set of polypropylene films is used to simulate the increasing amount of hydrogen, and the scattered intensity is monitored. From this response, an unknown amount of the hydrogen can be deduced empirically. We have further attempted a first principle calculation of the intensity of the scattered signal from the experimental systems, and have obtained good agreement between calculation and the measurements. The study can be used as a reference for future applications of the scattering method to other hydrogen-in-metal systems.

Both neutron-powder-diffraction and neutron-vibrational-spectroscopy studies have been undertaken to characterize the structures and vibrational dynamics of a variety of bulk hcp rareearth trihydrides RH3 (where R = Y, Th, Dy, Ho, Er, and Lu). The results are consistent with P3c1 as the prevalent structural symmetry for all trihydrides investigated except LuH3. Corresponding results for LuH3 are suggestive of an atypical arrangement of H atoms. Preliminary analyses of LuD3 diffraction patterns indicate that the main peaks can be satisfactorily modeled using P63/mmc symmetry with a reduced unit cell, although numerous minor diffraction features and a relatively unusual vibrational spectrum hint at either a more complex structure or an unknown secondary phase. The deviations from P3c1 symmetry are likely a consequence of the relatively smaller metal-hydrogen bond distances for LuH3.

Titanium has a strong chemical affinity and can absorb and store large amounts of hydrogen, which causes embrittlement of the material. Ion implantation is applied to improve wear behavior e.g. of titanium alloys, which are used for load bearing components of hip and knee joint prostheses. Nitrogen implantation influences the hydrogen content in the near surface region of a commercially available pure titanium. 150 keV 15N-ions were implanted at RT into titanium samples with a fluence of 6 × 1017 ions/cm2 and subsequently annealed at 500°C under high vacuum conditions. For comparison N was also implanted at a sample temperature of 500°C. Concentration depth profiles of implanted nitrogen and accumulated hydrogen were measured with Nuclear Reaction Analysis (NRA) and compared to nitrogen and titanium depth profiles obtained with X-ray Photoelectron Spectroscopy (XPS). The results indicate a relation between hydrogen concentration and the formation of Ti-N bonds.

Migration of protons dissolved in acceptor doped SrZrO3, SrCeO3 and BaCeO3 oxides has been examined under an applied electric potential over a range of temperature from 25 to 220°C. Protons which dissolved in these oxides migrated to the cathode, and they were trapped there when the cathode material had a good ability to getter the migrating hydrogen. The amount of hydrogen accumulated in the cathode could be measured by the ERDA method using a highenergy 4He beam. We measured the amount of hydrogen in the cathode while monitoring the dc current passed through the oxide specimen. The proton transport number was determined from the ratio of the number of hydrogen in the cathode to the total numbers of charge through the specimen. The diffusion coefficient of proton was evaluated using the proton transport number and proton concentration in the specimen.

Local vibrational mode (LVM) spectroscopy of hydrogen and deuterium in GaP, AlSb, ZnSe, and GaN has provided important information about the structures of dopanthydrogen complexes and their interaction with the host lattice. In GaN:Mg, for example, hydrogen binds to a host nitrogen which is adjacent to the magnesium acceptor. In GaP and ZnSe, it has been demonstrated that the temperature dependent shifts of LVM's are proportional to the lattice thermal energy, a consequence of the anharmonic coupling of the local mode to acoustical phonons.

Large hydrostatic pressures have been applied to semiconductors to probe the vibrational properties of hydrogen-related complexes. In GaAs, the pressure dependent shifts of the 12C-H and 13C-H stretch modes have positive curvatures, while the shift of the S-H stretch mode has a negative curvature. This may be related to the fact that in the bond-centered C-H complex, the hydrogen is compressed between the carbon acceptor and one gallium host atom, whereas in the S-H complex, the hydrogen occupies an interstitial position and is not crowded by neighboring atoms. If these trends are general, then hydrostatic pressure may be a powerful tool in determining the position of the hydrogen atom(s) in a complex.

In AISb. pressure was utilized to resolve a mystery as to why the Se-D complex gives rise to one stretch mode peak while the Se-H stretch mode splits into three peaks. This anomalous splitting is explained in terms of a new resonant interaction between the stretch mode and combination modes involving a wag mode harmonic and extended lattice phonons. The interaction gives rise to vibrational modes with both localized and extended components. When the temperature or hydrostatic pressure is varied, the modes exhibit anti-crossing behavior.

Hydrogen is an important component of the gas phase growth chemistry for GaN (eg. NH3, (CH 3)3 Ga)and the processing environment for subsequent device fabrication (eg. SiH4 for dielectric deposition, NH3 or H2 annealing ambients), and is found to readily permeate into heteroepitaxial material at temperatures ≤200°C. Its main effect has been the passivation of Mg acceptors in p-GaN through formation of neutral Mg-H complexes, which can be dissociated through minority-carrier (electron) injection or simple thermal annealing. Atomic hydrogen is also found to passivate a variety of other species in GaN, as detected by a change in the electrical or optical properties of the material. An example is the increase in luminescence efficiency of Er3+ ions in AIN after hydrogenation, through passivation of non-radiative states that would be an alternative path for de-excitation. The injection of hydrogen during a large variety of device fabrication steps has been detected by SIMS profiling using 2H isotopic labeling. Basically all of the acceptor species in GaN, namely Mg, C, Ca and Cd are found to form complexes with hydrogen.

In order to explain the effects of hydrogen on the electrical properties of bulk indium phosphide crystals, we have performed a series of high temperature annealing studies with both undoped and iron-doped indium phosphide crystals. Our samples were annealed at 900°C for 6, 36, and 72 hours, respectively, under a phosphorus overpressure of five atmospheres. Samples were characterized at 10 K by Fourier transform infrared absorption spectroscopy which allowed us to measure the concentrations of both the Fe2+ and VIn-H4 defects simultaneously. Undoped samples were further characterized by the Hall effect measurements. We find in the iron-doped samples that the [Fe2+]/[Fe3+] ratio decreases gradually with increasing annealing time, indicating a reduction in the number of donors in the samples. In the undoped samples, annealing leads to a reduction of the free electron concentration accompanied by an increase in the 77 K mobility. The increase of the sample's mobility eliminates the possibility that the reduction of the free electron concentration is due to an increase in the concentration of the compensating acceptors. Our explanation for the observed behavior in all samples is that hydrogen acts as a donor and it diffuses out of the crystal during the annealing process. Based on our experimental data, we propose a calibration equation of [VIn-H4] = 4.2×1016 cm−1 × Absorbance (cm−1) which is used to correlate the hydrogen-vacancy complex concentrations with the changes of the VIn-H4 absorption peak in both the iron-doped and the undoped samples. Our results confirm the donor nature of the hydrogen-vacancy complex and provide strong evidence regarding the reduction mechanism of free carrier concentrations in bulk indium phosphide crystals during high temperature annealing under a phosphorus atmosphere.

Complexes of vacancy at indium site with one to four hydrogen atoms and isolated hydrogen or hydrogen dimer and other infrared absorption lines, tentatively be assigned to hydrogen related defects were investigated by FTIR. Hydrogen can passivate imperfections, thereby eliminating detrimental electronic states from the energy bandgap.Incorporated hydrogen can introduce extended defects and generate electrically-active defects. Hydrogen also can acts as an actuator for creating of antistructure defects. Isolated hydrogen related defects(e.g. H12+) may play an important role in the conversion of the annealed wafers from semiconducting to the semi-insulating behavior. H2+ may be a deep donor, whose energy level is very near the iron deep acceptor level in the energy gap.

High quality Al0.3Ga0.7As/GaAs quantum wells with centrally doped Be-acceptors were grown by molecular beam epitaxy (MBE). The well width is either 10 nm or 20 nm, and the concentration of Be-acceptors is varied between 5× 1016/cm3 and 2×1018/cm3. The structures were treated systematically by dc H-plasma at different sample temperatures, gas pressures and cooling down procedures. The passivation of Be-acceptors were characterized by photoluminescence spectroscopy and secondary ion mass spectrometry (SIMS). Without causing degradation of the A1GaAs/GaAs interfaces, we have obtained, for the first time, a deactivation of above 80% of the Be-acceptors. The influence of the Be-doping on the bandgap excitons in the QW structures is also investigated in detail. A significant difference is found in comparison with the earlier reports for 150 Å wide quantum wells, in which different samples were used for different doping concentrations.

The hydrogen-related metastable defects (M31M4) in n-GaAs, first found by Buchwald et al., were introduced only in the crystals containing the EL2 center. Off-center oxygen (=EL3), could not be responsible for their formation. A quantitative analysis with the samples exposed to atomic hydrogen showed that the M4 defect consisted of two different configurations. One of them did couple with M3, but is latent in the as-exposed state. It was formed after bias annealing at higher temperatures, such as 420 K. The other part of the M4 defect (M4•) existed at room temperature and after annealing at 513K, but disappeared and reappeared upon forward- and reverse-bias annealings, respectively.

Hydrogen incorporation in both undoped and nitrogen-doped CdTe and ZnSe is investigated. Evidence for a strong nitrogen-hydrogen interaction is presented. Preliminary data indicate that the growth of CdTe and ZnSe under an atomic hydrogen flux results in a significant concentration of paramagnetic defects possibly accompanied by enhanced auto-doping from residual impurities.

To introduce atomic hydrogen into Cu-chalcopyrite samples, low energy broad beam ion implantation into heated targets was used. In addition to the expected hydrogen diffusion into the sample from the implanted thin surface layer, another hydrogen-related effect was observed. As demonstrated for single crystalline CuInSe2, at target temperatures above 150°C a surface layer becomes In-rich. Two phases, the CuInSe2 α-phase and a In-rich phase similar to the reported ordered vacancy compounds (β-phase) coexist, as detected by Raman spectroscopy. The depth profile and the thermal stability of this hydrogen-related compositional variation are investigated. Based on the results we discuss a model of this effect, involving a copper in-diffusion, caused by the hydrogenation due to filling of Cu vacancies and possible substitution of Cu by H. The observed β-phase-like compound is unstable against annealing above 180°C, but can be restored in a thermal cycling process. Annealing for 1.5 h at 400°C removes it completely and restores the asgrown CuInSe2 surface. A decrease of the hydrogen concentration in the surface layer due to redistribution and out-diffusion, followed by the recovery of the Cu content, might be responsible for this behaviour.

We implanted at 300 eV into Cu-chalcopyrite semiconductors at temperatures between 50°C and 300°C. The surface chemistry is similar to the previously reported behavior of CuInS2 implanted with a H2+, H+ low energy ion beam [1] with respect to secondary phase etching. We also found an increase of radiative recombination (photoluminescence), which had been attributed to defect passivation and, hence, as an indicator of hydrogen incorporation [2]. Under the 300 eV implantation conditions, however, we observed neither a hydrogen concentration in a few hundred nm surface range exceeding the NRA detection limit of about 1×1019 cm-3 nor a pronounced stoichiometry variation in the ternary material, as proved by Raman measurements.

We conclude, therefore, that a 300 eV implantation introduces significantly less atomic hydrogen into the volume of the sample than previously reported for other beam compositions under similar temperature and current density conditions. This could be a result of the very low energy of less than 100 eV which can be expected for atomic H produced by dissociation of 300 eV at the surface, making the instant out-diffusion into the high vacuum of the implantation chamber a favored process.

Mass-fraction standards of dilute hydrogen in titanium alloy are prepared by direct reaction of the elements, and verified by cold-neutron prompt-gamma activation analysis. The procedure is applied to the production and characterization of Standard Reference Materials.

A study of hydrogen cycling-induced phase segregation in AB5-type intermetallics is presented. Influence of temperature for the alloy compositions Yni4AI, LaNi5, Ce0.5La0.5Ni5 and Ce0.7La0.3Ni5 is shown. Morphology of the nanostructured particles formed is studied and discussed.

SCC of 304 stainless steel(ss) in boiling MgCl2 at 416K was performed to investigated the effect of hydrogen during test. Results showed that the existence of hydrogen enhanced the susceptibility of SCC of 304ss. The fractography of specimen charged with hydrogen contained more intergranular than that of uncharged ones, and for the both specimens charged or uncharged with hydrogen, SCC initiated and propagated along { 111 } plane.