Hydrogen In Crystalline Silicon Research Articles

Hydrogen Gettering and Platelet Formation in Implanted and Hydrogenated Silicon

The trapping of hydrogen in crystalline silicon at a buried defect layer has been investigated by Raman scattering spectroscopy. The defect concentration of the trap layer was created by various implantation doses of hydrogen ions. Hydrogen was additionally inserted by subsequent plasma exposure at various temperatures. The basic platelet formation and hydrogen trapping mechanisms are investigated with regard to the use for hydrogen induced silicon layer exfoliation. The analyzed results exhibit that the platelet formation mechanism highly depends on the hydrogenation temperature and on the vacancy concentration.

A technique to study the lattice location of light elements in silicon by channeling elastic recoil detection analysis

We reported an ion beam analysis technique to detect the lattice location of hydrogen in crystalline silicon by the method of channeling elastic recoil detection analysis. In this technique, the incident beam is introduced along low index channeling axes while the sample is tilted to an angle by which the forward-scattered H atoms can be detected. We have applied this technique to study the lattice location of 1H trapped within a boron-doped Si layer.

Evidence for a trigonal dimer of antibonding hydrogen in crystalline silicon

The infrared absorption spectra recorded on silicon crystals implanted with protons at cryogenic temperatures reveal three lines at 812, 1608, and $1791\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$, which originate from the excitation of local vibrational modes of a H defect. Measurements carried out on crystals subjected to uniaxial stress show that the $812\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ line results from excitation of a two-dimensional mode of a trigonal defect. Based on the analysis of the experimental data and on comparison with the properties of other known H defects in Si, we ascribe the 812 and $1791\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ lines to a wag mode and a stretch mode of a defect with one or more H atoms at antibonding sites and attached to neighboring Si atoms. A likely structure denoted ${\mathrm{H}}_{2}^{**}$ is proposed, where each one of two nearest neighboring Si atoms forms a bond with one H so that the two Si-H bonds point in opposite directions towards interstitial tetrahedral sites along the same ⟨111⟩ axis.

Electronic levels of isolated and oxygen-perturbed hydrogen in silicon and migration of hydrogen

The migration of monatomic hydrogen in crystalline silicon is governed by three potential energy surfaces corresponding to the three possible charges states of hydrogen. The H 0 and H + surfaces have minima at the bond-centre site (BC) and give rise to a donor state, whereas the H − surface has minimum at the interstitial tetrahedral site (T) giving rise to an acceptor state. We review the current experimental status regarding these surfaces. The BC-donor and the T-site acceptor are found to exist in two closely related forms, which we explain by a distortion of the energy surfaces when hydrogen is trapped in the silicon lattice at the nearby interstitial oxygen. We show how this oxygen distortion acts as a catalyst for the conversion from H − at T sites to H + at BC sites and retards the migration of H + through BC sites.

Depth profiling of hydrogen in crystalline silicon using elastic recoil detection analysis

Accurate depth profiling of hydrogen in crystalline silicon (c-Si) from reflection elastic recoil detection analysis (ERDA) can be performed using a method that converts the channel difference between surface and bulk signals directly to depth. The method relies on Rutherford backscattering spectrometry (RBS) to unambiguously determine the depth of a buried marker coincident with a hydrogen distribution in each of several silicon calibration standards. A conversion from ERDA channels to depth is extracted from the relationship between the depth to the marker and the channel difference between surface and bulk hydrogen centroids in forward recoil spectra acquired simultaneously. Applying this conversion to ERDA of hydrogen-implanted c-Si taken under the same conditions as those of the silicon calibration standards results in accurate, quantitative depth profiling. A comparison of techniques shows that this method offers distinct advantages over depth profiling by computer simulation of ERDA spectra.

Vibrational dynamics of bond-center hydrogen in crystalline silicon

The absorption line shape associated with the fundamental transition of the H-related stretch mode of bond-center hydrogen in crystalline silicon is measured as a function of temperature with infrared spectroscopy. In addition to the shift in frequency and increase in linewidth usually observed for local vibrational modes in solids, the absorption line becomes asymmetric at elevated temperatures. A theoretical model is developed, which describes the temperature-dependent line shape in terms of thermal fluctuations in the occupation number of a low-frequency mode coupled anharmonically to the stretch mode. The model successfully describes the shift, broadening, and asymmetry of the absorption line and gives new insight into the nature of the low-frequency mode. The mode has a frequency of 114cm{sup -1}, is twofold degenerate, and exhibits no isotopic shift when deuterium is substituted for hydrogen. It is assigned to a pseudolocalized, Si-related mode of bond-center hydrogen.

Vibrational lifetime of bond-center hydrogen in crystalline silicon

The lifetime of the stretch mode of bond-center hydrogen in crystalline silicon is measured to be T1 = 7.8+/-0.2 ps with time-resolved, transient bleaching spectroscopy. The low-temperature spectral width of the absorption line due to the stretch mode converges towards its natural width for decreasing hydrogen concentration C(H), and nearly coincides with the natural width for C(H) approximately 1 ppm. The lifetimes of the Si-H stretch modes of selected hydrogen-related defects are estimated from their spectral widths and shown to range from 1.6 to more than 37 ps.

Diffusion of hydrogen in crystalline silicon

The coefficient of diffusion of hydrogen in crystalline silicon is calculated using tight-binding molecular dynamics. Our results are in good quantitative agreement with an earlier study by Panzarini and Colombo [Phys. Rev. Lett. 73, 1636 (1994)]. However, while our calculations indicate that long jumps dominate over single hops at high temperatures, no abrupt change in the diffusion coefficient can be observed with decreasing temperature. The (classical) Arrhenius diffusion parameters, as a consequence, should extrapolate to low temperatures.

First-principles study of the quantum states of muonium and hydrogen in crystalline silicon

We present a theoretical study of the quantum states of muonium and atomic hydrogen in crystalline silicon using the generalized gradient approximation to density-functional theory combined with the path-integral molecular-dynamics method. Normal muonium, one of the two stable states, is distributed around the tetrahedral site. The potential-energy surface is considerably modified in the presence of muonium by distorting silicon cage and stabilizes the state. The other state of muonium, anomalous muonium, is located around the bond center site with significant quantum vibration in a steep potential well. The relative stabilities and dynamics of the two sites are discussed, and the essential roles of quantum effects are emphasized.

Quantum Distributions of Muonium and Hydrogen in Crystalline Silicon

Quantum states of normal muonium and atomic hydrogen in crystalline silicon are investigated with the path integral molecular dynamics method using interatomic potentials based on the density functional theory. It is shown that, in spite of instability in the potential energy surface, muonium has a high density at the center of the silicon cage ( $T$ site) due to quantum effect in agreement with previous $\ensuremath{\mu}$SR experiments. A distinct and more classical distribution is suggested for hydrogen.

Defect-induced dissociation ofH2in silicon

Ab initio molecular-dynamics simulations of intrinsic defects and hydrogen in crystalline silicon reveal an unexpected process with considerable implications. The vacancy $(V)$ and the self-interstitial $(I),$ both rapid diffusers in $c\ensuremath{-}\mathrm{Si},$ dissociate interstitial ${\mathrm{H}}_{2}$ molecules with a substantial gain in energy: $V+{\mathrm{H}}_{2}\ensuremath{\rightarrow}{V,\mathrm{H},\mathrm{H}}+4.0\mathrm{eV}$ and $I+{\mathrm{H}}_{2}\ensuremath{\rightarrow}{I,\mathrm{H},\mathrm{H}}+1.7\mathrm{eV}.$ The dissociation of ${\mathrm{H}}_{2}$ is caused by the lattice strain associated with the defect, and occurs whenever ${\mathrm{H}}_{2}$ molecules are in the vicinity of strained Si-Si bonds. After the dissociation, the two H's may either bind to the defect that caused the strain or diffuse away from it. The calculated Frenkel pair formation energy is 8.2 eV. The reaction ${\mathrm{H}}_{2}{+\mathrm{H}}_{2}\ensuremath{\rightarrow}{V,{\mathrm{H}}_{4}}+I$ releases less than 0.1 eV, suggesting that ${\mathrm{H}}_{2}$'s in otherwise perfect Si will not generate intrinsic defects.

Electronically Induced Instability of a Hydrogen-Carbon Complex in Silicon and Its Dissociation Mechanism

We studied, by deep-level transient spectroscopy (DLTS), the dissociation mechanism of a hydrogen-carbon (H-C) complex, which has a donor level at E c-0.15 eV and acts as an electron trap in crystalline silicon. On the basis of our results and a previously proposed atomic model of the H-C complex, in which the hydrogen atom resides inside a silicon-carbon bond, we have proposed the following dissociation mechanism. The complex is stable in the positive charge state, and to dissociate it needs a hydrogen jump with an activation energy of 1.3 eV to break the bond with carbon and silicon. The complex becomes neutral by capturing an electron from the conduction band or accepting an electron directly from the valence band under electronic excitation, and is consequently dissociated at an activation energy of 0.5 eV due to the loss of binding. Strong evidence for the existence of the negative charge state of hydrogen in crystalline silicon is also presented.

Theoretical study of the arsenic-hydrogen complex in silicon

Abstract The microscopic structure of a complex formed by arsenic, silicon and hydrogen in crystalline silicon has been studied. Density functional calculations with a numerical atomic orbital basis have been performed for a (SiH3)3As SIH(Si3H5)3 cluster. The potential energy surface of the passivating hydrogen has been calculated and the vibrational frequencies for hydrogen isotopes have been determined by a numerical integration of the Schrodinger equation. The results are compared to those obtained previously by means of other methods. Furthermore, the influence of gradient corrections to the local density approximation has been investigated.

Coupling of Electronic and Structural Properties of Hydrogen in Crystalline Silicon

AbstractTheory has made great progress during recent years in calculating the fundamental properties of monatomic hydrogen in crystalline silicon. By applying the DLTS and DDLTS method we use the hydrogen-carbon complex which consists of an electronically inactive carbon atom on a substitutional lattice site and a hydrogen atom near the bond-center position to detect theoretically predicted properties of hydrogen in silicon. The results of two independent experiments show that there exists a coupling of the electronic and structural properties of monatomic hydrogen, as predicted by theory.

Tight-binding quantum molecular-dynamics simulations of hydrogen in silicon.

We have carried out molecular-dynamics simulations of neutral hydrogen in crystalline silicon using tight-binding (TB) quantum-mechanical total energies and forces. A well-established model due to Goodwin et al. is used for the Si-Si interactions. For the Si-H interactions, we have fit our Harrison-type TB model to the known properties of silane and to both theoretical and experimental information about hydrogen in crystalline silicon. Several simulations performed in the temperature range of 1050 to 2000 K yield a diffusion curve in good agreement with experiment. The H diffusion is found to be jumplike between bond-centered (BC) sites, and the trapping of H at the BC site is mediated by a metastable onefold coordinated H configuration which weakens adjacent Si-Si bonds, allowing the H to enter the BC site. Vibrational frequencies for hydrogen at the BC site are also calculated and isotopic frequency shifts are discussed.

Local Bonding Structure of Hydrogen in Crystalline Silicon: NMR and Tem Studies

ABSTRACTNuclear magnetic resonance (NMR) and transmission electron microscopy have been used to obtain information on the local structure of deuterium in single-crystal silicon, both for deuterated, phosphorous-doped Si that contains platelet-structured defects and for deuterated boron-doped silicon. In both cases, the NMR spectrum consists of two components, a narrow doublet and a central, unsplit line. The doublet arises from D bonded to Si with the Si-D bond along the <111> directions. The central line, which contains more D than does the doublet, is ascribed primarily to molecular D2 that resides in regions of the crystal where translation and tumbling are inhibited and possibly to some D in weak Si-D bonds.

Deep state of hydrogen in crystalline silicon: Evidence for metastability.

After proton implantation into n-type silicon at 45 K, a bistable hydrogen center with a band-gap level ${\mathit{E}}_{\mathit{c}}$-${\mathit{E}}_{\mathit{t}}$=0.16 eV is observed by deep-level transient spectroscopy. The center anneals at \ensuremath{\sim}100 K under zero bias with a decay constant \ensuremath{\nu}=(3.0\ifmmode\times\else\texttimes\fi{}${10}^{12}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$)exp[(-0.29 eV)/${\mathit{k}}_{\mathit{B}}$T] and at \ensuremath{\sim}210 K under reverse bias with \ensuremath{\nu}=(1.3\ifmmode\times\else\texttimes\fi{}${10}^{8}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$)exp[(-0.44 eV)/${\mathit{k}}_{\mathit{B}}$T]. In both cases the center regenerates by forward-bias injection at low temperatures. The decay without (with) reverse bias reflects capture of one (two) electron(s). The metastability is ascribed to hydrogen jumps between bond-center and tetrahedral sites as a result of changes in charge states.

States of hydrogen in crystalline silicon

The thermal transformation of deuterium in p-type crystalline silicon is studied with a variety of experimental techniques. It is found that D-atoms initially trapped at acceptor sites can be transferred by low temperature annealing to a different state tentatively ascribed to interstitial D2 molecules. Diffusion of D out of the passivated sample only occurs at temperatures significantly higher than this transformation temperature. This fact allows us to produce Si samples with extremely high deuterium concentrations (several at%) by a suitable passivation-annealing sequence. With increasing D-concentration, a number of characteristic Si-D defect complexes have been observed by vibrational spectroscopy.

Charge state of hydrogen in crystalline silicon.

An estimate is given for the relative stabilities of neutral and positive bond-center hydrogen interstitials and of negatively charged hydrogen at the antibonding site as a function of Fermi-level position. We predict the hydrogen-related donor level to be below the intrinsic Fermi level, and the existence of a Fermi-energy region around midgap where the neutral charge state is stable.

Hydrogen dissolution in and release from nonmetals. II. Crystalline silicon

The solubility of hydrogen in crystalline silicon from 1363–1473 K and from 1.7–9.2 atm has been measured using the method of high-temperature, high-pressure infusion followed by high-temperature vacuum outgassing with mass-spectrometric detection. The measured solubilities were in the range 1–5×1016 atoms/cm3 and exhibited a temperature dependence consistent with a heat of solution of 30–40 kcal/mole. The pressure dependence of the solubility was consistently smaller than the square-root dependence characteristic of simple interstitial solution. The release-rate curves showed multiple peaks, which are incompatible with the classical diffusion model of release. Instead the peaks correspond to trapping of hydrogen at distinct binding sites in the silicon lattice. The release kinetics were modeled as detrapping processes.