The effect of deposition temperature on the morphology and optoelectronic performance of Ge/Si QDs grown by magnetron sputtering under low Ge deposition(~4 nm)was investigated by atomic force microscopy,Raman spectros...The effect of deposition temperature on the morphology and optoelectronic performance of Ge/Si QDs grown by magnetron sputtering under low Ge deposition(~4 nm)was investigated by atomic force microscopy,Raman spectroscopy,and photoluminescence(PL)tests.The experimental results indicate that temperatures higher than 750℃effectively increase the crystallization rate and surface smoothness of the Si buffer layer,and temperatures higher than 600℃significantly enhance the migration ability of Ge atoms,thus increasing the probability of Ge atoms meeting and nucleating to form QDs on Si buffer layer,but an excessively high temperature will cause the QDs to undergo an Ostwald ripening process and thus develop into super large islands.In addition,some PL peaks were observed in samples containing small-sized,high-density Ge QDs,the photoelectric properties reflected by these peaks were in good agreement with the corresponding structural characteristics of the grown QDs.Our results demonstrate the viability of preparing high-quality QDs by magnetron sputtering at high deposition rate,and the temperature effect is expected to work in conjunction with other controllable factors to further regulate QD growth,which paves an effective way for the industrial production of QDs that can be used in future devices.展开更多
The single event effect(SEE) sensitivity of silicon–germanium heterojunction bipolar transistor(Si Ge HBT) irradiated by 100-Me V proton is investigated. The simulation results indicate that the most sensitive positi...The single event effect(SEE) sensitivity of silicon–germanium heterojunction bipolar transistor(Si Ge HBT) irradiated by 100-Me V proton is investigated. The simulation results indicate that the most sensitive position of the Si Ge HBT device is the emitter center, where the protons pass through the larger collector-substrate(CS) junction. Furthermore, in this work the experimental studies are also carried out by using 100-Me V proton. In order to consider the influence of temperature on SEE, both simulation and experiment are conducted at a temperature of 93 K. At a cryogenic temperature, the carrier mobility increases, which leads to higher transient current peaks, but the duration of the current decreases significantly.Notably, at the same proton flux, there is only one single event transient(SET) that occurs at 93 K. Thus, the radiation hard ability of the device increases at cryogenic temperatures. The simulation results are found to be qualitatively consistent with the experimental results of 100-Me V protons. To further evaluate the tolerance of the device, the influence of proton on Si Ge HBT after gamma-ray(^(60)Coγ) irradiation is investigated. As a result, as the cumulative dose increases, the introduction of traps results in a significant reduction in both the peak value and duration of the transient currents.展开更多
The effect of strains on the thermal conductivity of Si/Ge superlattices was investigated by nonequilibrium molecular dynamics（NEMD） simulation. The thermal conductivities experienced a near linear drop with increas...The effect of strains on the thermal conductivity of Si/Ge superlattices was investigated by nonequilibrium molecular dynamics（NEMD） simulation. The thermal conductivities experienced a near linear drop with increasing tensile and compressive strains. It was explained by the fact that the decrease of the phonons velocities and a mass of structural defects generated under strains. Meanwhile, a theoretical calculation based on Modified-Callaway model was performed,and it was found that the theoretical results were in good agreement with the molecular dynamics results.展开更多
Lattice dynamics of strained(Si)_(4)/(Ge)_(4) superlattice grown pseudomorphically on (001)-oriented Si_(1-x)Ge_(x)(0≤x≤1)substrate is investigated.In the present calculations,the effects of strain and substrate are...Lattice dynamics of strained(Si)_(4)/(Ge)_(4) superlattice grown pseudomorphically on (001)-oriented Si_(1-x)Ge_(x)(0≤x≤1)substrate is investigated.In the present calculations,the effects of strain and substrate are discussed.展开更多
Silicon is emerging as a promising next-generation lithium-ion battery anode because of its high theoretical capacity and low cost.However,the poor cyclability and inferior rate performance hinder its largescale appli...Silicon is emerging as a promising next-generation lithium-ion battery anode because of its high theoretical capacity and low cost.However,the poor cyclability and inferior rate performance hinder its largescale applications.Here,hollow silicon/germanium(H-SiGe)nanospheres with a binary-active component and heterogeneous structure combined with porous carbon(pC)reinforcing are synthesized as lithium-ion battery anodes.Experimental studies demonstrate that the H-SiGe/pC anodes possess tiny volume expansion,high ion/electron conductivity,and stable electrode interface.Theoretical calculations confirm that through the replacement of Si using Ge with rational component control,the diffusion energy barrier of lithium will be reduced and lithium storage ability can be improved because of the slight charge polarization.Benefiting from these unique merits,the H-SiGe/pC anodes display a high initial specific capacity of 2922.2 mA h g^(-1)at 0.1 A g^(-1),superior rate capability(59.4%capacity retention from 0.5 to 8 A g^(-1)),and excellent cycling stability(81%retention after 700 cycles at 5 A g^(-1)at 1.0–1.2 mg cm^(-2)).An outstanding stability is preserved even at a high loading of 3.2 mg cm^(-2)with an improved reversible capacity of 429.1 mA h g^(-1)after 500 cycles at 4 A g^(-1).Furthermore,the full-cell with the prelithiated H-SiGe/pC anode and LiFePO4cathode exhibits an impressive capacity performance.展开更多
Calculation shown that the refraction index of Ge_0.6Si_0.4/Sistrained-layer superlattice n≈3.64, when L_w=9 nm and L_b=24 nm. Analgorithm of numerical iteration for effective refraction index isemployed to obtain di...Calculation shown that the refraction index of Ge_0.6Si_0.4/Sistrained-layer superlattice n≈3.64, when L_w=9 nm and L_b=24 nm. Analgorithm of numerical iteration for effective refraction index isemployed to obtain different effective refraction indexes atdifferent thickness (L). As a result, the thickness ofGe_0.6Si_0.4/Si strained-layer superlattice optical waveguide, L≤363nm, can be determined, which is very important for designingwaveguide devices. An optical waveguide can be made into a nanometerdevice by using Ge_0.6 Si_0.4/Si strained-layer superlattice.展开更多
According to Maxwell’s theory, the optical transmission characteristics in GeSi/Si superlattice nanocrystalline layer have been analyzed and calculated. The calculated result shows that when the total thickness L is ...According to Maxwell’s theory, the optical transmission characteristics in GeSi/Si superlattice nanocrystalline layer have been analyzed and calculated. The calculated result shows that when the total thickness L is 340nm, the single mode lightwave can be transmitted only at periodic number M≥15.5. In addition, at the direction of transmission, when the transmission distance is larger than 500μm, the lightwave intensity is decreased greatly. Based on the above parameters, the design and manufacture of GeSi/Si superlattice nanocrystalline photodetector are carried out.展开更多
CaN films with an AlxGa1-xN/AlyGa1-xN superlattice （SL） buffer layer are grown on Si（111） substrates by metal-organic chemical vapor deposition （MOCVD）. The structure and strain properties of the samples are stu...CaN films with an AlxGa1-xN/AlyGa1-xN superlattice （SL） buffer layer are grown on Si（111） substrates by metal-organic chemical vapor deposition （MOCVD）. The structure and strain properties of the samples are studied by optical microscopy, Raman spectroscopy, x-ray diffractometry and atomic force microscopy. The results show that the strain status and crystalline quality of the CaN layers are strongly dependent on the difference of the Al composition between AlxCa1-xN barriers and AlyCa1-yN wells in the SLs. With a large Al composition difference, the CaN film tends to generate cracks on the surface due to the severe relaxation of the SLs. Otherwise, when using a small Al composition difference, the crystalline quality of the CaN layer degrades due to the poor function of the SLs in filtering dislocations. Under an optimized condition that the Al composition difference equals 0.1, the crack-free and compressive strained CaN film with an improved crystalline quality is achieved. Therefore, the AlxGa1-xN/AlyGal-yN SL buffer layer is a promising buffer structure for growing thick CaN films on Si substrates without crack generation.展开更多
基金Founded by the National Key Research and Development Program(No.2021YFB3802400)the National Natural Science Foundation of China(No.52161037)the Basic Research Project of Yunnan Province(No.202001AU070112)。
文摘The effect of deposition temperature on the morphology and optoelectronic performance of Ge/Si QDs grown by magnetron sputtering under low Ge deposition(~4 nm)was investigated by atomic force microscopy,Raman spectroscopy,and photoluminescence(PL)tests.The experimental results indicate that temperatures higher than 750℃effectively increase the crystallization rate and surface smoothness of the Si buffer layer,and temperatures higher than 600℃significantly enhance the migration ability of Ge atoms,thus increasing the probability of Ge atoms meeting and nucleating to form QDs on Si buffer layer,but an excessively high temperature will cause the QDs to undergo an Ostwald ripening process and thus develop into super large islands.In addition,some PL peaks were observed in samples containing small-sized,high-density Ge QDs,the photoelectric properties reflected by these peaks were in good agreement with the corresponding structural characteristics of the grown QDs.Our results demonstrate the viability of preparing high-quality QDs by magnetron sputtering at high deposition rate,and the temperature effect is expected to work in conjunction with other controllable factors to further regulate QD growth,which paves an effective way for the industrial production of QDs that can be used in future devices.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.61574171,61704127,11875229,51872251,and 12027813)。
文摘The single event effect(SEE) sensitivity of silicon–germanium heterojunction bipolar transistor(Si Ge HBT) irradiated by 100-Me V proton is investigated. The simulation results indicate that the most sensitive position of the Si Ge HBT device is the emitter center, where the protons pass through the larger collector-substrate(CS) junction. Furthermore, in this work the experimental studies are also carried out by using 100-Me V proton. In order to consider the influence of temperature on SEE, both simulation and experiment are conducted at a temperature of 93 K. At a cryogenic temperature, the carrier mobility increases, which leads to higher transient current peaks, but the duration of the current decreases significantly.Notably, at the same proton flux, there is only one single event transient(SET) that occurs at 93 K. Thus, the radiation hard ability of the device increases at cryogenic temperatures. The simulation results are found to be qualitatively consistent with the experimental results of 100-Me V protons. To further evaluate the tolerance of the device, the influence of proton on Si Ge HBT after gamma-ray(^(60)Coγ) irradiation is investigated. As a result, as the cumulative dose increases, the introduction of traps results in a significant reduction in both the peak value and duration of the transient currents.
基金Supported by the National Natural Science Foundation of China(No.51706039)
文摘The effect of strains on the thermal conductivity of Si/Ge superlattices was investigated by nonequilibrium molecular dynamics（NEMD） simulation. The thermal conductivities experienced a near linear drop with increasing tensile and compressive strains. It was explained by the fact that the decrease of the phonons velocities and a mass of structural defects generated under strains. Meanwhile, a theoretical calculation based on Modified-Callaway model was performed,and it was found that the theoretical results were in good agreement with the molecular dynamics results.
文摘Lattice dynamics of strained(Si)_(4)/(Ge)_(4) superlattice grown pseudomorphically on (001)-oriented Si_(1-x)Ge_(x)(0≤x≤1)substrate is investigated.In the present calculations,the effects of strain and substrate are discussed.
基金supported by the National Natural Science Foundation of China programs(52007110,22078179,21901146)the Natural Science Foundation of Shandong Province(ZR2020QB048)the Taishan Scholar Foundation(tsqn201812063)。
文摘Silicon is emerging as a promising next-generation lithium-ion battery anode because of its high theoretical capacity and low cost.However,the poor cyclability and inferior rate performance hinder its largescale applications.Here,hollow silicon/germanium(H-SiGe)nanospheres with a binary-active component and heterogeneous structure combined with porous carbon(pC)reinforcing are synthesized as lithium-ion battery anodes.Experimental studies demonstrate that the H-SiGe/pC anodes possess tiny volume expansion,high ion/electron conductivity,and stable electrode interface.Theoretical calculations confirm that through the replacement of Si using Ge with rational component control,the diffusion energy barrier of lithium will be reduced and lithium storage ability can be improved because of the slight charge polarization.Benefiting from these unique merits,the H-SiGe/pC anodes display a high initial specific capacity of 2922.2 mA h g^(-1)at 0.1 A g^(-1),superior rate capability(59.4%capacity retention from 0.5 to 8 A g^(-1)),and excellent cycling stability(81%retention after 700 cycles at 5 A g^(-1)at 1.0–1.2 mg cm^(-2)).An outstanding stability is preserved even at a high loading of 3.2 mg cm^(-2)with an improved reversible capacity of 429.1 mA h g^(-1)after 500 cycles at 4 A g^(-1).Furthermore,the full-cell with the prelithiated H-SiGe/pC anode and LiFePO4cathode exhibits an impressive capacity performance.
文摘Calculation shown that the refraction index of Ge_0.6Si_0.4/Sistrained-layer superlattice n≈3.64, when L_w=9 nm and L_b=24 nm. Analgorithm of numerical iteration for effective refraction index isemployed to obtain different effective refraction indexes atdifferent thickness (L). As a result, the thickness ofGe_0.6Si_0.4/Si strained-layer superlattice optical waveguide, L≤363nm, can be determined, which is very important for designingwaveguide devices. An optical waveguide can be made into a nanometerdevice by using Ge_0.6 Si_0.4/Si strained-layer superlattice.
文摘According to Maxwell’s theory, the optical transmission characteristics in GeSi/Si superlattice nanocrystalline layer have been analyzed and calculated. The calculated result shows that when the total thickness L is 340nm, the single mode lightwave can be transmitted only at periodic number M≥15.5. In addition, at the direction of transmission, when the transmission distance is larger than 500μm, the lightwave intensity is decreased greatly. Based on the above parameters, the design and manufacture of GeSi/Si superlattice nanocrystalline photodetector are carried out.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61076120 and 61106130the Natural Science Foundation and Scientific Support Plan of Jiangsu Province under Grant Nos BK2012516,BK20131072,and BE2012007
文摘CaN films with an AlxGa1-xN/AlyGa1-xN superlattice （SL） buffer layer are grown on Si（111） substrates by metal-organic chemical vapor deposition （MOCVD）. The structure and strain properties of the samples are studied by optical microscopy, Raman spectroscopy, x-ray diffractometry and atomic force microscopy. The results show that the strain status and crystalline quality of the CaN layers are strongly dependent on the difference of the Al composition between AlxCa1-xN barriers and AlyCa1-yN wells in the SLs. With a large Al composition difference, the CaN film tends to generate cracks on the surface due to the severe relaxation of the SLs. Otherwise, when using a small Al composition difference, the crystalline quality of the CaN layer degrades due to the poor function of the SLs in filtering dislocations. Under an optimized condition that the Al composition difference equals 0.1, the crack-free and compressive strained CaN film with an improved crystalline quality is achieved. Therefore, the AlxGa1-xN/AlyGal-yN SL buffer layer is a promising buffer structure for growing thick CaN films on Si substrates without crack generation.
