Optical characterization of damage and concentration profiles in H ion implanted amorphous silicon

Heidemann, Klaus; Grüner, Matilda; Kaat, E. te

doi:10.1080/00337578408206088

Cited by 21 publications

(7 citation statements)

References 24 publications

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“…A host of other techniques has shown that structural relaxation is accompanied by a reduction in the defect density of 2%, namely isothermal and scanning calorimetry, 49 positron spectroscopy, 50 Pd solubility and diffusivity measurements, 51 and hydrogen trapping. 45 This strongly implies that the increase in coordination number is a direct consequence of the reduction in defect density and reinforces our earlier conclusion that the final undercoordination indicates a remaining vacancy density of about 1.5%. However, it raises the question why structural relaxation is not accompanied by densification.…”

Section: Structural Relaxation and Defect Annihilationsupporting

confidence: 89%

“…To put these two extreme views in context, we first realize that an isolated danglingbond density of 12% is clearly much higher than what is experimentally observed. It is known from optical absorption, 45 electrical, 46 SAXS, 47 and combined Raman and positron lifetime measurements, 48 that only a few at. % H is required to saturate all dangling bonds.…”

Section: Atomic Structure Of Annealed Amorphous Si Materialsmentioning

confidence: 99%

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High-energy x-ray diffraction study of pure amorphous silicon

et al. 1999

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Medium and high-energy x-ray diffraction has been used to study the atomic structure of pure amorphous Si prepared by MeV Si implantation into crystalline silicon. Both as-implanted and annealed samples were studied. The inelastically scattered x rays were removed by fitting the energy spectrum for the scattered x rays. The atomic scattering factor of silicon, previously known reliably up to 20 Å Ϫ1 , has been extended to 55 Å Ϫ1. The radial distribution function of amorphous Si, before and after annealing, has been determined through an unbiased Fourier transformation of the normalized scattering data. Gaussian fits to the first neighbor peak in these functions shows that scattering data out to at least 40 Å Ϫ1 is required to reliably determine the radial distribution function. The first-shell coordination number increases from 3.79 to 3.88 upon thermal annealing at 600°C, whereas that of crystalline Si determined from similar measurements on a Si powder analyzed using the same technique is 4.0. Amorphous Si is therefore under coordinated relative to crystalline Si. Noise in the distribution function, caused by statistical variations in the scattering data at high-momentum transfer, has been reduced without affecting the experimental resolution through filtering of the interference function after subtracting the contribution of the first-neighbor peak. The difference induced by thermal annealing in the remainder of the radial distribution functions, thus revealed, is much smaller than previously believed. ͓S0163-1829͑99͒00943-1͔ I. INTRODUCTION

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Section: Structural Relaxation and Defect Annihilationsupporting

confidence: 89%

Section: Atomic Structure Of Annealed Amorphous Si Materialsmentioning

confidence: 99%

High-energy x-ray diffraction study of pure amorphous silicon

et al. 1999

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“…The 2% change in C 1 upon thermal annealing is consistent with other experimental work, which has shown that the positron spectra [18], Pd solubility and diffusivity [19], and hydrogen trapping [20] all change upon thermal annealing according to a decrease of 2 at. % of trapping sites, i.e., defects.…”

supporting

confidence: 90%

“…We thus conclude that all visible changes in the first and second neighbor peaks induced by thermal annealing are consistent with the annihilation of 2 at. % point defects, which is in excellent and quantitative agreement with a range of other experiments characterizing structural relaxation [18][19][20][21].…”

supporting

confidence: 86%

High Resolution Radial Distribution Function of Pure Amorphous Silicon

et al. 1999

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The structure factor S͑Q͒ of high purity amorphous Si membranes prepared by ion implantation was measured over an extended Q range (0.03 55 Å 21). Calculation of the first neighbor shell coordination (C 1) as a function of maximum Q indicates that measurement of S͑Q͒ out to at least 40 Å 21 is required to reliably determine the radial distribution function (RDF). A 2% change in C 1 and subtle changes in the rest of the RDF were observed upon annealing, consistent with point defect removal. After annealing at 600 ± C, C 1 3.88, which would explain why amorphous Si is less dense than crystalline Si.

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“…Several studies have shown that hydrogen implanted into Si, either amorphous or crystalline, is initially mobile, forms bonds with Si, and passivates dangling bonds, even at temperatures well below room temperature [9][10][11][12]. Near the peak of the proton implantation profile, the hydrogen concentration is nearly 10 at.…”

Section: Discussion: Limit On the Diffusivity Of Interstitially Dissomentioning

confidence: 99%

Upper limit on room-temperature diffusion of metal impurities interstitially dissolved in amorphous Si

Diop

Roorda

2014

Can. J. Phys.

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Impurity profiles of Cu and Ag in amorphous silicon were studied before and after one year storage at room temperature and found to be indistinguishable. Since just before storage, hydrogen had been ion implanted into the uniformly metal doped layer, a diffusivity in excess of 3 × 10 −24 m 2 /s would have led to an observable change in the impurity profile. Therefore the room-temperature diffusivity must be less than that (3 × 10 −24 m 2 /s), which in turn implies one of two possibilities: either the interstitial diffusivity is much lower than previously determined, or the metal impurities were not fully detrapped by the implanted hydrogen. A subsequent thermal anneal at 450°C confirmed that the detrapping and diffusion of Ag and Cu in H-implanted amorphous Si conforms to its normal behaviour. The low value of the room-temperature diffusivity is important for the interpretation of forthcoming measurements on high-energy ion tracks in amorphous Si. PACS Nos.: 66.30.J-, 71.55.Jv, 61.72.uf, 81.05.Gc.Résumé : Nous avons étudié les profils d'impureté de Cu et de Ag dans du silicium amorphe, avant et après remisage d'un an à la température de la pièce et nous observons qu'ils sont indiscernables. L'implantation ionique d'hydrogène dans la couche dopée métalliquement aurait causé un changement observable dans les profils d'impureté si le coefficient de diffusion avait été plus grand que 3 × 10 −24 m 2 /s. Ce coefficient est donc plus petit que 3 × 10 −24 m 2 /s, ce qui implique deux possibilités. Soit que la diffusivité est plus faible que déterminée précédemment, soit que les impuretés métalliques n'ont pas été libérées de leur piège par l'hydrogène. Un recuit subséquent à 450°C confirme que la libération et la diffusion de Ag et Cu dans du Si amorphe avec implantation de H sont conformes au comportement normal. La basse valeur du coefficient de diffusion à la température de la pièce est importante dans l'interprétation de mesures à venir de trajectoires d'ions de haute énergie dans du Si amorphe. [Traduit par la Rédaction]

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Optical characterization of damage and concentration profiles in H ion implanted amorphous silicon

Cited by 21 publications

References 24 publications

High-energy x-ray diffraction study of pure amorphous silicon

High-energy x-ray diffraction study of pure amorphous silicon

High Resolution Radial Distribution Function of Pure Amorphous Silicon

Upper limit on room-temperature diffusion of metal impurities interstitially dissolved in amorphous Si

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