We found that device-quality thin films of amorphous oxide semiconductor, a-In-Ga-Zn-O, unintentionally include high-density hydrogens over 1020 cm−3 but the electron concentration remains low at ~1015 cm−3 in as-deposited states. The hydrogens exist in the form of hydroxyl group –OH, but most of them are inactive as an electron donor, which is explained by charge compensation due to incorporation of excess oxygens. Although their diffusions are fast compared with those in crystalline ZnO, but oxygen can diffuse only 20 nm even at 400°C. Hydrogen diffusion is much faster, and easily hydrogenizes a thin channel of a thin-film transistor.

https://iopscience.iop.org/article/10.1149/2.011301jss/pdf

Effects of Diffusion of Hydrogen and Oxygen on Electrical Properties of Amorphous Oxide Semiconductor, In-Ga-Zn-O

We have developed a single-wafer vacuum encapsulation for microelectromechanical systems (MEMS), using a thick (20-mum) polysilicon encapsulation to package micromechanical resonators in a pressure 600 cycles of -50 to 80degC, and no measurable change in cavity pressure was seen. We have also performed accelerated leakage tests by driving hydrogen gas in and out of the encapsulation at elevated temperature. Two results have come from these hydrogen diffusion tests. First, hydrogen diffusion rates through the encapsulation at temperatures 300-400degC have been determined. Second, the package was shown to withstand multiple temperature cycles between room and 300-400degC without showing any adverse affects. The high robustness and stability of the encapsulation can be attributed to the clean, high-temperature environment during the sealing process

/pdf/long-term-and-accelerated-life-testing-of-a-novel-single-3ylhgpsftp.pdf

Long-Term and Accelerated Life Testing of a Novel Single-Wafer Vacuum Encapsulation for MEMS Resonators

In this work, the stability and mobility of protonic defects in acceptor doped BaZrO3 are investigated using density functional theory in conjunction with kinetic modeling. The interaction between the mobile protons and Zr-site substituted trivalent dopants—Ga, Sc, In, Y, and Gd—is assessed by extensive mapping of migration pathways. In all cases, the interaction is attractive, which results in a stabilization, and hence a reduction of the mobility, of the proton. However, its strength and range vary substantially and are found to be strongly correlated to the ionic radius of the dopant. Further, it is shown that the observed correlation is related to a variation in strength of hydrogen bonds formed between protons and next nearest lattice oxygen ions in different environments. Finally, migration barriers and attempt frequencies obtained from first principles are used as input to a jump-diffusion model. The proton self-diffusion coefficient is evaluated for the different substituted phases, and the experimental trend in activation energies is reproduced.

Effect of acceptor dopants on the proton mobility in BaZrO3: A density functional investigation

Annealing at moderate temperatures is required to activate the silicon surface passivation by Al2O3 thin films while also the thermal stability at higher temperatures is important when Al2O3 is implemented in solar cells with screenprinted metallization. In this paper, the relationship between the microstructure of the Al2O3 film, hydrogen diffusion, and defect passivation is explored in detail for a wide range of annealing temperatures. The chemical passivation was studied using stacks of thermally-grown SiO2 and Al2O3 synthesized by atomic layer deposition. Thermal effusion measurements of hydrogen and implanted He and Ne atoms were used to elucidate the role of hydrogen during annealing. We show that the passivation properties were strongly dependent on the annealing temperature and time and were significantly influenced by the Al2O3 microstructure. The latter was tailored by variation of the deposition temperature (Tdep = 50 °C–400 °C) with hydrogen concentration [H] between 1 and 13 at.% and mass den...

/pdf/influence-of-annealing-and-al2o3-properties-on-the-hydrogen-g4db7ygtn5.pdf

Influence of annealing and Al2O3 properties on the hydrogen-induced passivation of the Si/SiO2 interface

The solar wind implants protons into the top 20–30 nm of lunar regolith grains, and the implanted hydrogen will diffuse out of the regolith but also interact with oxygen in the regolith oxides. We apply a statistical approach to estimate the diffusion of hydrogen in the regolith hindered by forming temporary bonds with regolith oxygen atoms. A Monte Carlo simulation was used to track the temporal evolution of bound OH surface content and the H2 exosphere. The model results are consistent with the interpretation of the Chandrayaan‐1 M3 observations of infrared absorption spectra by surface hydroxyls as discussed in Li and Milliken (2017, https://doi.org/10.1126/sciadv.1701471). The model reproduced the latitudinal concentration of OH by using a Gaussian energy distribution of f(U(sub 0) = 0.5 eV, U(sub W) = 0.078–0.1 eV) to characterize the activation energy barrier to the diffusion of hydrogen in space weathered regolith. In addition, the model results of the exospheric content of H2 are consistent with observations by the Lyman Alpha Mapping Project on the Lunar Reconnaissance Orbiter. Therefore, we provide support for hydroxyl formation by chemically trapped solar wind protons.

/pdf/solar-wind-implantation-into-the-lunar-regolith-monte-carlo-2lozsxhmni.pdf

Solar Wind Implantation Into the Lunar Regolith: Monte Carlo Simulations of H Retention in a Surface With Defects and the H2 Exosphere

Depth profiles of hydrogen implanted into crystalline silicon in random direction at different fluences have been measured by the15N technique and by SIMS. Whereas hydrogen implanted at a fluence of 1015 ions/cm2 shows some limited mobility, no such mobility is observed for higher implantation fluences. In these cases, ballistic computer codes describe the depth distributions well, within the ranges of both experimental and theoretical accuracy. Annealing up to 510 K does not change the hydrogen distributions.

Hydrogen implantation and diffusion in silicon and silicon dioxide

Films of SrYb 0.05 Zr 0.095 O 2.975 were prepared by sol-gel processing. Water vapour pressure/hydrogen composition isotherms were recorded ex-situ comprising pressures between 0 and 84.5 kPa and temperatures between 873 and 1073 K. Nuclear Resonance Reaction Analysis (NRRA) was used to determine the hydrogen concentration and, in addition, depth profiles of hydrogen concentration. The chemical potential of interstitial hydrogen in oxides could be determined; from its temperature dependence thermodynamical constants were calculated. We observe two hydrogen fractions with a site energy difference of 20 kJ/mol. A size effect of the thermodynamic properties is observed below a thickness of 350 nm: nanofilms exhibit higher solubility than bulk material.

Pressure/composition isotherms of proton conducting SrYb0.05Zr0.95O2.975/H2O by means of nuclear resonance reaction analysis

Various elements - H, Li, B, Ar, Kr, Xe, Cs, Pb and Bi - have been implanted at 20 - 200 keV and at room temperature up to different fluences into thin fullerene layers evaporated onto polished Si substrates. Subsequently their depth profiles were determined by NRA, NDP, or RBS analysis. These measurements were compared with ion implantation into amorphous carbon and with theory. In most cases the degree of fullerene destruction was monitored by Raman spectroscopy earlier. The results show that there exists a general trend insofar as theory appears to underestimate both ranges and range stragglings for heavy projectile ions, whereas for light and medium-heavy ions experimental range results agree with theory within some 30%. In a few cases range stragglings are found to be considerably larger than predicted by theory, which may be attributed to post-implantational radiation enhanced diffusion. There is only little influence of the degree of fullerene destruction onto the implantation profile para...

Ion Implantation into Fullerene

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Hydrogen implantation and diffusion in silicon and silicon dioxide

Pressure/composition isotherms of proton conducting SrYb0.05Zr0.95O2.975/H2O by means of nuclear resonance reaction analysis

Ion Implantation into Fullerene