Strain relaxation mechanism for hydrogen-implanted Si1−xGex/Si(100) heterostructures

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226

The kinetics of the switching process in Cu–SiO2-based electrochemical metallization memory cells was investigated as a function of the switching voltage and the SiO2 film thickness. We observe an exponential dependence of the switching rate on the switching voltage and no significant thickness dependence in the range from 5to20nm SiO2. We conclude from our data that the cathodic electrodeposition represents the rate-limiting step of the switching kinetics. The voltage-time dilemma seems to be overcome by the exponential dependence of the switching rate in combination with a threshold voltage presumably originating from a nucleation overpotential.

mentioning

confidence: 99%

Electrode kinetics of Cu–SiO2-based resistive switching cells: Overcoming the voltage-time dilemma of electrochemical metallization memories

Schindler

Staikov

Waser

2009

304

226

“…We have recently shown that this can be efficiently achieved by He + ion implantation and subsequent thermal annealing. 5,6 In a model of this process, 6 we have assumed that the narrow defect band formed upon ion implantation underneath the SiGe/ Si-substrate interface provides a high density of dislocation loops during annealing, part of which glides to the interface and evolves from there into dislocation arms consisting of segments of misfit dislocations ͑MDs͒ in the interface and threading dislocations ͑TDs͒ through the strained SiGe layer. The stress driven propagation of the TD segments through the SiGe layer along the ͓110͔ and ͓−110͔ directions is associated with an extension of the corresponding MD segments involving an increasing strain relaxation.…”

mentioning

confidence: 99%

Asymmetric strain relaxation in patterned SiGe layers: A means to enhance carrier mobilities in Si cap layers

Buca

Holländer

Feste

et al. 2007

Self Cite

Strain relaxation in patterned Si0.77Ge0.23 stripes grown on Si(001) by chemical vapour deposition was investigated after He+ ion implantation and annealing. Ion channeling measurements indicate asymmetric strain relaxation with a significantly higher residual strain parallel to the stripes than perpendicular to the stripes. These results are confirmed by plan view transmission electron microscopy showing a much higher density of misfit dislocations running along the stripes than across the stripes. Estimates based on a piezoresistivity model indicate significant enhancements of electron and hole mobilities for asymmetrically strained Si cap layers on such SiGe stripes.

“…As shown previously, He-filled cavities, underneath the SiGe layer are responsible for the formation of dislocation loops which glide towards the interface. 4 Under compressive plane stress in SiGe, one segment of such a loop is held at the interface where it forms a MD segment while the other one is driven through the SiGe layer towards the SiGe/ Si top interface.…”

Section: ͑1͒mentioning

confidence: 99%

“…It provides a high density of dislocation loops as sources for misfit dislocations (MDs) yielding efficient strain relaxation during annealing with low densities of threading dislocations (TDs). 3,4 For the strain transfer we make use of the propagation of the dislocations from the bottom of the relaxing SiGe layer towards the surface into the Si cap. This process differs from purely thermally induced strain relaxation where low densities of dislocations are nucleated randomly at the surface.…”

mentioning

confidence: 99%

Tensely strained silicon on SiGe produced by strain transfer

Buca

Holländer

Trinkaus

et al. 2004

Self Cite

An approach for the controlled formation of thin strained silicon layers based on strain transfer in an epitaxial Si/ SiGe/ Si͑100͒ heterostructure during the relaxation of the SiGe layer is established. He + ion implantation and annealing is employed to initiate the relaxation process. The strain transfer between the two epilayers is explained as an inverse strain relaxation which we modeled in terms of the propagation of the dislocations through the layers. Effcient strain buildup in the Si top layer strongly depends on the Si top layer thickness and on the relaxation degree of the SiGe buffer. This letter presents a process for strain transfer within an epitaxial Si/ SiGe/ Si͑100͒ heterosystem and the involved theoretical rationale. As strained silicon ͑sSi͒ permits a significant improvement of nanoelectronic devices, due to a large enhancement of the mobility of the electrons and holes, this material presently receives enormous interest. 1 Our approach permits the formation of a sSi layer by epitaxial growth of a thin ϳ200 nm heterosystem, unlike the most common approach, which involves the growth of a thick (several m) relaxed SiGe buffer layer, and the polishing and overgrowth of the strained layer. 2 Here, a cubic Si/strained SiGe/ Si͑100͒ heterostructure is formed first. Then the elastic energy stored in the pseudomorphic Si 1−x Ge x layer is relaxed in a controlled way to transform the cubic top layer into sSi. In order to initiate this inverse strain relaxation process a He + implantation into the Si͑100͒ substrate and an annealing step are conducted. During this process a narrow defect band underneath the SiGe/ Si substrate interface is generated. It provides a high density of dislocation loops as sources for misfit dislocations (MDs) yielding efficient strain relaxation during annealing with low densities of threading dislocations (TDs). 3,4 For the strain transfer we make use of the propagation of the dislocations from the bottom of the relaxing SiGe layer towards the surface into the Si cap. This process differs from purely thermally induced strain relaxation where low densities of dislocations are nucleated randomly at the surface. We model the strain buildup in the Si layer by considering the forces acting on the dislocations and their resulting motion through the layers in detail. Our approach also differs from strain transfer between a film and a compliant substrate where only limited areas can be transformed and the misfit strain is diluted due to the elastic energy balance the two layers. 5