“…This sample surface area can be called a porous SiGe layer. The formation of the surface morphology similar to that of the porous layers was previously observed after the high-temperature annealing of Si(111) substrates covered with Ge [ 16 ]. Fig.…”
Section: Resultssupporting
confidence: 60%
“…Nevertheless, there are significant differences in the porous SiGe layer formation on Si(100) and Si(111). On Si(111), the radical transformation in the surface morphology occurred quickly under annealing at temperatures above 700 °C and for any deposited Ge coverage studied (up to 150 nm) [ 16 ]. Whereas, the porous SiGe layer formation on Si(100) began from the sample edges and the boundary between the continuous and porous layers moved slowly to the sample center with the rate of ~10 μm/min.…”
Section: Resultsmentioning
confidence: 99%
“…As suggested here, the porous SiGe layer formation is the result of surface melting which is significantly facilitated by the strong stain caused by the Si-Ge lattice mismatch. It can also be suggested that the same reason is responsible for the porous SiGe layer formation on Si(111) [ 16 , 22 ]. Under annealing at temperatures in the range from 700 to 900 °C, two processes compete with each other.…”
Section: Resultsmentioning
confidence: 99%
“…The strain reduction can be achieved by the formation of more homogeneous distribution of chemical composition by means of Si-Ge intermixing under high-temperature annealing. Annealing can also produce significant changes in the surface morphology [ 16 ]. The temperature effects were studied with respect to compositional atomic ordering and surface morphology evolution for the SiGe islands prepared by the deposition of relatively low Ge coverages (up to several nm) [ 17 , 18 ].…”
We study the surface morphology and chemical composition of SiGe layers after their formation under high-temperature annealing at 800–1100 °C of 30–150 nm Ge layers deposited on Si(100) at 400–500 °C. It is found that the annealing leads to the appearance of the SiGe layers of two types, i.e., porous and continuous. The continuous layers have a smoothened surface morphology and a high concentration of threading dislocations. The porous and continuous layers can coexist. Their formation conditions and the ratio between their areas on the surface depend on the thickness of deposited Ge layers, as well as on the temperature and the annealing time. The data obtained suggest that the porous SiGe layers are formed due to melting of the strained Ge layers and their solidification in the conditions of SiGe dewetting on Si. The porous and dislocation-rich SiGe layers may have properties interesting for applications.
“…This sample surface area can be called a porous SiGe layer. The formation of the surface morphology similar to that of the porous layers was previously observed after the high-temperature annealing of Si(111) substrates covered with Ge [ 16 ]. Fig.…”
Section: Resultssupporting
confidence: 60%
“…Nevertheless, there are significant differences in the porous SiGe layer formation on Si(100) and Si(111). On Si(111), the radical transformation in the surface morphology occurred quickly under annealing at temperatures above 700 °C and for any deposited Ge coverage studied (up to 150 nm) [ 16 ]. Whereas, the porous SiGe layer formation on Si(100) began from the sample edges and the boundary between the continuous and porous layers moved slowly to the sample center with the rate of ~10 μm/min.…”
Section: Resultsmentioning
confidence: 99%
“…As suggested here, the porous SiGe layer formation is the result of surface melting which is significantly facilitated by the strong stain caused by the Si-Ge lattice mismatch. It can also be suggested that the same reason is responsible for the porous SiGe layer formation on Si(111) [ 16 , 22 ]. Under annealing at temperatures in the range from 700 to 900 °C, two processes compete with each other.…”
Section: Resultsmentioning
confidence: 99%
“…The strain reduction can be achieved by the formation of more homogeneous distribution of chemical composition by means of Si-Ge intermixing under high-temperature annealing. Annealing can also produce significant changes in the surface morphology [ 16 ]. The temperature effects were studied with respect to compositional atomic ordering and surface morphology evolution for the SiGe islands prepared by the deposition of relatively low Ge coverages (up to several nm) [ 17 , 18 ].…”
We study the surface morphology and chemical composition of SiGe layers after their formation under high-temperature annealing at 800–1100 °C of 30–150 nm Ge layers deposited on Si(100) at 400–500 °C. It is found that the annealing leads to the appearance of the SiGe layers of two types, i.e., porous and continuous. The continuous layers have a smoothened surface morphology and a high concentration of threading dislocations. The porous and continuous layers can coexist. Their formation conditions and the ratio between their areas on the surface depend on the thickness of deposited Ge layers, as well as on the temperature and the annealing time. The data obtained suggest that the porous SiGe layers are formed due to melting of the strained Ge layers and their solidification in the conditions of SiGe dewetting on Si. The porous and dislocation-rich SiGe layers may have properties interesting for applications.
“…7,8 In the case of dewetting, strain energy minimization additionally occurs through the formation of Si substrate areas that are not covered with SiGe films, thus reducing the size of interface areas between the deposited film and the substrate. 9 The dewetting in a Si-Ge system can induce the formation of submicron-and micron-sized SiGe particles on Si substrates, 6 which can serve as dielectric particles with a refractive index n > 3. The light scattering on such particles leads to the generation of electrical and magnetic resonances, according to Mie theory, when the relation d $ k/n between the particle size (d) and the wavelength of light (k) is satisfied.…”
High temperature annealing of thick (40-100 nm) Ge layers deposited on Si(100) at $400 C leads to the formation of continuous films prior to their transformation into porous-like films due to dewetting. The evolution of Si-Ge composition, lattice strain, and surface morphology caused by dewetting is analyzed using scanning electron microscopy, Raman, and photoluminescence (PL) spectroscopies. The Raman data reveal that the transformation from the continuous to porous film proceeds through strong Si-Ge interdiffusion, reducing the Ge content from 60% to about 20%, and changing the stress from compressive to tensile. We expect that Ge atoms migrate into the Si substrate occupying interstitial sites and providing thereby the compensation of the lattice mismatch. Annealing generates only one type of radiative recombination centers in SiGe resulting in a PL peak located at about 0.7 and 0.8 eV for continuous and porous film areas, respectively. Since annealing leads to the propagation of threading dislocations through the SiGe/Si interface, we can tentatively associate the observed PL peak to the well-known dislocation-related D1 band.
The promising and versatile applications of low dimensional materials are largely due to their surface properties, which along with their underlying electronic structures have been well studied. However, these materials may not be directly useful for applications requiring properties other than their natal ones. In recent years, strain has been shown to be an additionally useful handle to tune the physical and chemical properties of materials by changing their geometric and electronic structures. The strategies for producing strain are summarized. Then, the electronic structure of quasi-two dimensional layered non-metallic materials (e.g., graphene, MX2, BP, Ge nanosheets) under strain are discussed. Later, the strain effects on catalytic properties of metal-catalyst loaded with strain are focused on. Both experimental and computational perspectives for dealing with strained systems are covered. Finally, an outlook on engineering surface properties utilizing strain is provided.
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