Non-linearity of diffusion in amorphous Si–Ge multilayers

Csík, A.; Beke, D.L.; Langer, G.A.; Erdélyi, Zoltán; Daróczi, Lajos; Kapta, K.; Kis-Varga, M.

doi:10.1016/s0042-207x(01)00133-6

Cited by 12 publications

(14 citation statements)

References 7 publications

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“…In the latter case one has also to check how element interdiffusion takes place and what could be the possible influence of the presence of H on it. By using small-angle X-Ray diffraction it was shown by some of the present authors that in amorphous Si/Ge multilayers prepared by DC magnetron sputtering and submitted to heat treatment the diffusion is very asymmetric because of the strong concentration dependence of the interdiffusion coefficient [17][18][19]. Silicon was seen to enter into the germanium layer but germanium could not diffuse into silicon.…”

Section: Introductionmentioning

confidence: 60%

AFM and TEM study of hydrogenated sputtered Si/Ge multilayers

Frigeri¹,

Nasi²,

Serényi

et al. 2009

Superlattices and Microstructures

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Multilayers of hydrogenated ultrathin (3 nm) amorphous a-Si and a-Ge layers prepared by sputtering have been studied by atomic force microscopy (AFM) and transmission electron microscopy (TEM) to check the influence of annealing on their structural stability. The annealed multilayers exhibit surface and bulk degradation with formation of bumps and craters whose density and size increase with increasing hydrogen content and/or annealing temperature and time. Bumps are due to the formation of H2 bubbles in the multilayer. The craters are bumps blown up very likely because of too high a gas pressure inside. The release of H from its bonds to Si and Ge occurs within cavities very likely present in the samples. The necessary energy is supplied by the heat treatment and by the recombination of thermally generated carriers. Results by energy filtered TEM on the interdiffusion of Si and Ge upon annealing are also presented

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Section: Introductionmentioning

confidence: 60%

AFM and TEM study of hydrogenated sputtered Si/Ge multilayers

Frigeri¹,

Nasi²,

Serényi

et al. 2009

Superlattices and Microstructures

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“…The slope of the curves can show that diffusion took place between the Si and Ge layers. The non-linearity of the time dependence of lnI/I o indicates that the diffusion coefficient strongly depends on the composition and/or significant stresses of diffusion origin were formed during the heat treatments [7]. Nevertheless some qualitative conclusions can be obtained from the comparison of the above decay curves.…”

Section: Resultsmentioning

confidence: 99%

“…In our previous works the thermal stability of non-hydrogenated Si/Ge multilayers [6,7] was extensively studied, but there is no information available in literature on the effect of hydrogen addition in the intermixing of Si and Ge layers.…”

Section: Introductionmentioning

confidence: 99%

Investigation of thermal stability of hydrogenated amorphous Si/Ge multilayers

Csík

Serényi

Erdélyi

et al. 2009

Vacuum

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Thermal stability of hydrogenated amorphous Si/Ge multilayers has been investigated by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Small-Angle X-Ray Diffraction (SAXRD) techniques. Amorphous H-Si/Ge multilayers were prepared by RF sputtering with 1.5 and 6 ml/min H 2 flow-rate. It is shown by Elastic Recoil Detection Analysis (ERDA) that the hydrogen concentration increased by increasing H 2 flowrate. Annealing of the samples was carried out at 400 and 450 o C for several hours. It has been observed that samples prepared with 6 ml/min flow-rate at both annealing temperatures underwent significant structural changes: the surface of the samples was visibly roughened, gas bubbles were formed and craters were created. The decay of the periodic structure of Si and Ge layers in these types of multilayers was faster than in non-hydrogenated samples.Samples prepared with 1.5 ml/min flow-rate have similar behaviour at 450 o C, but at 400 o C * Corresponding author. Fax: +36-52-416181 E-mail address: csik@atomki.hu (A. Csik) 2 the decay of the first order SAXRD peaks was slower than in case of the non-hydrogenated multilayers. Qualitatively the observed behaviour can be explained by the fast desorption of the saturated hydrogen, leading to the formation of bubbles and craters at 450 o C, as well as, at 400 o C in the sample with lower H-content, by the possible passivation of the dangling bonds resulting in a slowing down of the diffusion intermixing.

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“…For further discussion see Ref. 20. It is also interesting to note that surprisingly there is no classical ͑bulk͒ interdiffusion result published in crystalline Si/Ge system, 21 in which a similar diffusional asymmetry is expected.…”

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confidence: 95%

Interdiffusion in amorphous Si/Ge multilayers by Auger depth profiling technique

Csík

Langer

Beke

et al. 2001

Journal of Applied Physics

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It has been shown by the Auger depth profiling technique that the concentration profile at the initially sharp Si/Ge interface in amorphous Si/Ge multilayers shifted but remained still sharp after a heat treatment at 680 K for 100 h. At the same time the fast diffusion of Si resulted in the formation of an almost homogeneous Ge͑Si͒ amorphous solid solution, while there was practically no diffusion of Ge into the Si layer. This is direct evidence on the strong concentration dependence of the interdiffusion coefficient in amorphous Si/Ge system, and it is in accordance with the previous indirect result obtained from the measurements of the decay of the small angle Bragg peaks, as well as with finite difference simulations. © 2001 American Institute of Physics. ͓DOI: 10.1063/1.1331330͔Changes in atomic structures of amorphous semiconductors and their relationships to physical properties are currently of interest due to their useful optical and electronic features.1,2 Since most structural changes are related to atomic diffusion, any real understanding of the structural transformation, homogenization, etc., must be based on the knowledge of the diffusion processes. The study of diffusion in amorphous materials includes some difficulties. One of the main problems is related to the thermal stability of the amorphous phase; the diffusional measurements should be carried out at low temperatures for very short diffusion times in order to avoid structural changes due, e.g., to structural relaxation. Additionally, in amorphous semiconductors the mechanism of diffusion is also not fully understood.3-5 Thus, for example factors controlling the details of diffusional homogenization in amorphous Si/Ge multilayers are still under discussion. First of all the diffusional asymmetry ͑manifested in the strong concentration dependence of the interdiffusion coefficients͒, 6 the significant pore formation during the diffusional mixing, 7 and the possible role of diffusional stresses 8 are the most important factors indicating the need of a better understanding of the previous process.In this article interdiffusion in amorphous Si-Ge multilayered specimens is studied by Auger depth profiling. The primary objective of the present investigation is to observe the predicted asymmetric change of composition caused by the strong concentration dependence of the diffusion coefficients. Experimental results, obtained from small angle x-ray diffraction ͑SAXRD͒ measurements at different average compositions indicated a strong concentration dependence of the chemical diffusion parameters.9,10 Although such a strong concentration dependence inevitably should lead to a significant curvature on the ln(I/I 0 ) ͑I/I 0 is the normalized height of the first order SAXRD peak͒ versus time plots 11 ͑and to oscillatory behavior of the higher order peaks͒, later on the experimentally observed curvature was rather attributed by the same group to the effects of structural relaxation and coupling back effects of stresses of diffusional origin were also excluded....

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Non-linearity of diffusion in amorphous Si–Ge multilayers

Cited by 12 publications

References 7 publications

AFM and TEM study of hydrogenated sputtered Si/Ge multilayers

AFM and TEM study of hydrogenated sputtered Si/Ge multilayers

Investigation of thermal stability of hydrogenated amorphous Si/Ge multilayers

Interdiffusion in amorphous Si/Ge multilayers by Auger depth profiling technique

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