This paper discusses the influence of Sb/In ratio on the transport properties and crystal quality of the 200 nm InAs_(x)Sb_(1-x)thin film.The Sb content of InAs_(x)Sb_(1-x)thin film in all samples was verified by HRXR...This paper discusses the influence of Sb/In ratio on the transport properties and crystal quality of the 200 nm InAs_(x)Sb_(1-x)thin film.The Sb content of InAs_(x)Sb_(1-x)thin film in all samples was verified by HRXRD of the symmetrical 004 reflections and asymmetrical 115 reflections.The calculation results show that the Sb component was 0.6 in the InAs_(x)Sb_(1-x)thin film grown under the conditions of Sb/In ratio of 6 and As/In ratio of 3,which has the highest electron mobility(28560 cm^(2)/V·s)at 300 K.At the same time,the influence ofⅤ/Ⅲratio on the transport properties and crystal quality of Al_(0.2)In_(0.8)Sb/InAs_(x)Sb_(1-x)quantum well heterostructures also has been investigated.As a result,the Al_(0.2)In_(0.8)Sb/InAs_(0.4)Sb_(0.6)quantum well heterostructure with a channel thickness of 30 nm grown under the conditions of Sb/In ratio of 6 and As/In ratio of 3 has a maximum electron mobility of 28300 cm^(2)/V·s and a minimum RMS roughness of 0.68 nm.Through optimizing the growth conditions,our samples have higher electron mobility and smoother surface morphology.展开更多
High-quality antiferromagnetic(AFM)θ-phase manganese nitride(MnN)films were successfully grown on MgO(001)substrates by plasma-assisted molecular beam epitaxy.Structural analysis confirms the high-quality MnN film ha...High-quality antiferromagnetic(AFM)θ-phase manganese nitride(MnN)films were successfully grown on MgO(001)substrates by plasma-assisted molecular beam epitaxy.Structural analysis confirms the high-quality MnN film has a tetragonal distortion with a c/a ratio of~0.98.The film exhibits exceptional stability in both aqueous and ambient conditions,which is a crucial factor for practical applications.Electrical transport reveals its metallic behavior with an upturn at low temperatures,which could be attributed to the Kondo effect originated from nitrogen vacancy-induced magnetic impurities.Room temperature exchange bias has been demonstrated in a MnN/CoFeB heterostructure,verifying the AFM ordering of MnN.Considering its high Néel temperature~650 K,superior stability,and low-cost,this work highlights the epitaxial MnN films as a promising candidate for AFM spintronic applications.展开更多
We introduce our state-of-the art of“vacuum consistent electrochemistry”to an investigation of the interfaces between oxides and ionic liquid(IL).Pulsed laser deposition(PLD)has been one of the powerful and sophisti...We introduce our state-of-the art of“vacuum consistent electrochemistry”to an investigation of the interfaces between oxides and ionic liquid(IL).Pulsed laser deposition(PLD)has been one of the powerful and sophisticated techniques to realize nanoscale preparation of high-quality epitaxial oxide thin films.On the other hand,electrochemistry is a simple,very sensitive,and non-destructive analysis technique for solid-liquid interfaces.To ensure the reproducibility in experiment of the interfaces of such epitaxial oxide films,as well as bulk oxide single-crystals,with IL,we employ a home-built PLD-electrochemical(EC)system with IL as an electrolyte.The system allows one to perform all-in-vacuum experiments during the preparation of well-defined oxide electrode surfaces to their electrochemical analyses.The topics include electrochemical evaluations of the oxide’s own properties,such as carrier density and relative permittivity,and the interfacial properties of oxides in contact with IL,such as flat band potential and electric double layer(EDL)capacitance,ending with future perspectives in all-solid-state electrochemistry.展开更多
To improve quality and repeatability of GaAs growth on Si substrate,a new method named as four-step growth was proposed by successively inserting a low temperature(LT)and a high temperature(HT)GaAs buffer layer betwee...To improve quality and repeatability of GaAs growth on Si substrate,a new method named as four-step growth was proposed by successively inserting a low temperature(LT)and a high temperature(HT)GaAs buffer layer between the GaAs nucleation layer and the normal GaAs epilayer.The grown layers through four-step method showed high quality,i.e.single domain structure,mirror-like surface even under strong white light,reduced surface roughness and less surface defects,as well as high repeatability.Even without any post-growth annealing process,a 1μm thick GaAs epilayer with root mean square(RMS)roughness of only 2.1 nm in 5μm×5μm scanning areas was obtained while the full width at half maximum(FWHM)value of the GaAs(004)peak from double crystal X-ray diffractionω-scan was just 210.6 arcsec.展开更多
Interplay between topology and magnetism can give rise to exotic properties in topological materials.Two-dimensional bismuth has been extensively studied owing to its topological states with a strong spin-orbit coupli...Interplay between topology and magnetism can give rise to exotic properties in topological materials.Two-dimensional bismuth has been extensively studied owing to its topological states with a strong spin-orbit coupling,and 1T-VTe_(2)monolayer theoretically predicted to host an intrinsic magnetism as experimentally suggested.In this work,we successfully constructed a vertical heterostructure composed of the two-dimensional Bi(110)monolayer and 1T-VTe_(2)monolayer by using molecular beam epitaxy(MBE).Scanning tunneling microscopy(STM)measurements revealed that the growth of Bi preferably occurs along the step edges of the VTe_(2)monolayer,forming a Bi(110)monolayer on top of the VTe_(2)monolayer next to a peripheral Bi bilayer.The Bi(100)/VTe_(2)heterostructure exhibits a specific lattice registry with a well-defined moiréperiodicity.Scanning tunneling spectroscopy(STS)measurements further unveiled an universal suppression in the local density-of-states at the boundary of the Bi(110)/VTe_(2)bilayer.By examining the atomic structures of Bi(110)boundaries,we found this effect does not originate from the previously proposed atomic reconstruction at the step edge of Bi(110),but is likely related to the magnetic properties of the VTe_(2)monolayer.展开更多
Although it has a significant advantage in gain properties,the lack of selective etching processes hinders ZnO lasing in on-chip applications.Herein,the circular ZnO microdisk pivoted on Si substrate is fabricated thr...Although it has a significant advantage in gain properties,the lack of selective etching processes hinders ZnO lasing in on-chip applications.Herein,the circular ZnO microdisk pivoted on Si substrate is fabricated through depositing ZnO on patterned silicon on an insulator(SOI)substrate.The cavity structure,morphology,and photoluminescence(PL)properties are studied systematically.The cavity shows a well-defined circular structure with oxygen vacancies.Under the synergistic action of surface tension and stress,the ZnO microdisk shows a unique toroid structure with a high sidewall surface finish.The ZnO microcavity(8μm in diameter)shows optically pumped whispering gallery modes(WGMs)lasing in the ultraviolet region with a Q factor exceeding 1300.More interestingly,the quality of the toroid ZnO microdisk cavity is high enough to support the bandgap renormalization(BGR)phenomenon.With the increasing pumping power,the lasing spectra will be modulated.The lasing spectrum undergoes a Burstein-Moss(BM)effect-induced blueshift and an electron-hole plasma(EHP)effect-induced redshift.展开更多
Among the synthesis techniques for graphene,chemical vapor deposition(CVD)enables the direct growth of graphene films on insulating substrates.Its advantages include uniform coverage,high quality,scalability,and compa...Among the synthesis techniques for graphene,chemical vapor deposition(CVD)enables the direct growth of graphene films on insulating substrates.Its advantages include uniform coverage,high quality,scalability,and compatibility with industrial processes.Graphene is chemically inert and has a zero-bandgap which poses a problem for its use as a functional layer,and nitrogen doping has become an important way to overcome this.Post-plasma treatment has been explored for the synthesis of nitrogen-doped graphene,but the procedures are intricate and not suitable for large-scale production.We report the direct synthesis of nitrogen-doped graphene on a 4-inch sapphire wafer by ethanol-assisted CVD employing pyridine as the carbon feedstock,where the nitrogen comes from the pyridine and the hydroxyl group in ethanol improves the quality of the graphene produced.Additionally,the types of nitrogen dopant produced and their effects on III-nitride epitaxy were also investigated,resulting in the successful illumination of LED devices.This work presents an effective synthesis strategy for the preparation of nitrogen-doped graphene,and provides a foundation for designing graphene functional layers in optoelectronic devices.展开更多
A new type of 785 nm semiconductor laser device has been proposed.The thin cladding and mode expansion layer structure incorporated into the epitaxy on the p-side significantly impacts the regulation of grating etchin...A new type of 785 nm semiconductor laser device has been proposed.The thin cladding and mode expansion layer structure incorporated into the epitaxy on the p-side significantly impacts the regulation of grating etching depth.Thinning of the p-side waveguide layer makes the light field bias to the n-side cladding layer.By coordinating the confinement effect of the cladding layer,the light confinement factor on the p-side is regulated.On the other hand,the introduction of a mode expansion layer facilitates the expansion of the mode profile on the p side cladding layer.Both these factors contribute positively to reducing the grating etching depth.Compared to the reported epitaxial structures of symmetric waveguides,the new structure significantly reduces the etching depth of the grating while ensuring adequate reflection intensity and maintaining resonance.Moreover,to improve the output performance of the device,the new epitaxial structure has been optimized.Based on the traditional epitaxial structure,an energy release layer and an electron blocking layer are added to improve the electronic recombination efficiency.This improved structure has an output performance comparable to that of a symmetric waveguide,despite being able to have a smaller gain area.展开更多
Epitaxy is usually used to produce high quality crystals with ato-mic perfection. Up to now, many semiconductor crystals of functional materials could be obtained by epitaxial growth techniques, such as molecular beam...Epitaxy is usually used to produce high quality crystals with ato-mic perfection. Up to now, many semiconductor crystals of functional materials could be obtained by epitaxial growth techniques, such as molecular beam epitaxy, chemical vapor deposition, and liquid-phase epitaxy. However, these techniques are expensive, sophisticated, and not compatible with large area production. For solution-based deposition of epitaxial films such as hydrothermal processing [1], chemical bath deposition [2-3], and electrodeposition [4-5], specific conditions such as high temperature and pressure, or conducting substrates are commonly needed. Since single crystal epitaxial films have superior electronic and optical properties compared to amorphous and polycrystalline films due to absence of high-angle grain boundaries, searching for simple, rapid and inexpensive technique to grow epitaxial films is highly desired.展开更多
The Dzyaloshinskii‒Moriya interaction(DMI)at the interface of nonferromagnetic/ferromagnetic heterostructure films can induce the formation of chiral magnetic structures such as skyrmions,leading to the topological Ha...The Dzyaloshinskii‒Moriya interaction(DMI)at the interface of nonferromagnetic/ferromagnetic heterostructure films can induce the formation of chiral magnetic structures such as skyrmions,leading to the topological Hall effect(THE).Here,we report the first growth of high-quality La_(0.67)Sr_(0.33)MnO_(3)/Tb_(2)Ti_(2)O_(7)(LSMO/TTO)heterostructure films on single-crystal yttria-stabilized zirconia(111)substrates via laser molecular beam epitaxy.Electrical transport measurements reveal two key findings:(ⅰ)The anomalous Hall effect(AHE)of the LSMO/TTO heterostructure exhibits sign reversal within 50-100 K,and(ⅱ)a distinct hump signal emerges at low temperatures,differing from that of pure LSMO films.This hump signal weakens with increasing temperature,which is consistent with the characteristics of the THE.We propose that the THE-like signal originates from the LSMO lattice distortion induced by epitaxial growth on TTO,which breaks centrosymmetry and triggers DMI.Furthermore,the spin‒orbit coupling of Tb3+4f electrons likely generates interfacial spin currents,providing a driving force for the observed THE.展开更多
基金Supported by the Natural Science Basic Research Program of Shaanxi Province(2023-JC-QN-0758)Shaanxi University of Science and Technology Research Launch Project(2020BJ-26)Doctoral Research Initializing Fund of Hebei University of Science and Technology,China(1181476).
文摘This paper discusses the influence of Sb/In ratio on the transport properties and crystal quality of the 200 nm InAs_(x)Sb_(1-x)thin film.The Sb content of InAs_(x)Sb_(1-x)thin film in all samples was verified by HRXRD of the symmetrical 004 reflections and asymmetrical 115 reflections.The calculation results show that the Sb component was 0.6 in the InAs_(x)Sb_(1-x)thin film grown under the conditions of Sb/In ratio of 6 and As/In ratio of 3,which has the highest electron mobility(28560 cm^(2)/V·s)at 300 K.At the same time,the influence ofⅤ/Ⅲratio on the transport properties and crystal quality of Al_(0.2)In_(0.8)Sb/InAs_(x)Sb_(1-x)quantum well heterostructures also has been investigated.As a result,the Al_(0.2)In_(0.8)Sb/InAs_(0.4)Sb_(0.6)quantum well heterostructure with a channel thickness of 30 nm grown under the conditions of Sb/In ratio of 6 and As/In ratio of 3 has a maximum electron mobility of 28300 cm^(2)/V·s and a minimum RMS roughness of 0.68 nm.Through optimizing the growth conditions,our samples have higher electron mobility and smoother surface morphology.
文摘High-quality antiferromagnetic(AFM)θ-phase manganese nitride(MnN)films were successfully grown on MgO(001)substrates by plasma-assisted molecular beam epitaxy.Structural analysis confirms the high-quality MnN film has a tetragonal distortion with a c/a ratio of~0.98.The film exhibits exceptional stability in both aqueous and ambient conditions,which is a crucial factor for practical applications.Electrical transport reveals its metallic behavior with an upturn at low temperatures,which could be attributed to the Kondo effect originated from nitrogen vacancy-induced magnetic impurities.Room temperature exchange bias has been demonstrated in a MnN/CoFeB heterostructure,verifying the AFM ordering of MnN.Considering its high Néel temperature~650 K,superior stability,and low-cost,this work highlights the epitaxial MnN films as a promising candidate for AFM spintronic applications.
文摘We introduce our state-of-the art of“vacuum consistent electrochemistry”to an investigation of the interfaces between oxides and ionic liquid(IL).Pulsed laser deposition(PLD)has been one of the powerful and sophisticated techniques to realize nanoscale preparation of high-quality epitaxial oxide thin films.On the other hand,electrochemistry is a simple,very sensitive,and non-destructive analysis technique for solid-liquid interfaces.To ensure the reproducibility in experiment of the interfaces of such epitaxial oxide films,as well as bulk oxide single-crystals,with IL,we employ a home-built PLD-electrochemical(EC)system with IL as an electrolyte.The system allows one to perform all-in-vacuum experiments during the preparation of well-defined oxide electrode surfaces to their electrochemical analyses.The topics include electrochemical evaluations of the oxide’s own properties,such as carrier density and relative permittivity,and the interfacial properties of oxides in contact with IL,such as flat band potential and electric double layer(EDL)capacitance,ending with future perspectives in all-solid-state electrochemistry.
基金National Basic Research Program of China(2013CB632104)
文摘To improve quality and repeatability of GaAs growth on Si substrate,a new method named as four-step growth was proposed by successively inserting a low temperature(LT)and a high temperature(HT)GaAs buffer layer between the GaAs nucleation layer and the normal GaAs epilayer.The grown layers through four-step method showed high quality,i.e.single domain structure,mirror-like surface even under strong white light,reduced surface roughness and less surface defects,as well as high repeatability.Even without any post-growth annealing process,a 1μm thick GaAs epilayer with root mean square(RMS)roughness of only 2.1 nm in 5μm×5μm scanning areas was obtained while the full width at half maximum(FWHM)value of the GaAs(004)peak from double crystal X-ray diffractionω-scan was just 210.6 arcsec.
基金financially supported by the National Key Research and Development Program of China(Grant No.2021YFA1400403)the National Natural Science Foundation of China(Grant Nos.12374183,92165205)+2 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20233001)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302800)the Fundamental Research Funds for the Central Universities(Grant No.020414380207).
文摘Interplay between topology and magnetism can give rise to exotic properties in topological materials.Two-dimensional bismuth has been extensively studied owing to its topological states with a strong spin-orbit coupling,and 1T-VTe_(2)monolayer theoretically predicted to host an intrinsic magnetism as experimentally suggested.In this work,we successfully constructed a vertical heterostructure composed of the two-dimensional Bi(110)monolayer and 1T-VTe_(2)monolayer by using molecular beam epitaxy(MBE).Scanning tunneling microscopy(STM)measurements revealed that the growth of Bi preferably occurs along the step edges of the VTe_(2)monolayer,forming a Bi(110)monolayer on top of the VTe_(2)monolayer next to a peripheral Bi bilayer.The Bi(100)/VTe_(2)heterostructure exhibits a specific lattice registry with a well-defined moiréperiodicity.Scanning tunneling spectroscopy(STS)measurements further unveiled an universal suppression in the local density-of-states at the boundary of the Bi(110)/VTe_(2)bilayer.By examining the atomic structures of Bi(110)boundaries,we found this effect does not originate from the previously proposed atomic reconstruction at the step edge of Bi(110),but is likely related to the magnetic properties of the VTe_(2)monolayer.
文摘Although it has a significant advantage in gain properties,the lack of selective etching processes hinders ZnO lasing in on-chip applications.Herein,the circular ZnO microdisk pivoted on Si substrate is fabricated through depositing ZnO on patterned silicon on an insulator(SOI)substrate.The cavity structure,morphology,and photoluminescence(PL)properties are studied systematically.The cavity shows a well-defined circular structure with oxygen vacancies.Under the synergistic action of surface tension and stress,the ZnO microdisk shows a unique toroid structure with a high sidewall surface finish.The ZnO microcavity(8μm in diameter)shows optically pumped whispering gallery modes(WGMs)lasing in the ultraviolet region with a Q factor exceeding 1300.More interestingly,the quality of the toroid ZnO microdisk cavity is high enough to support the bandgap renormalization(BGR)phenomenon.With the increasing pumping power,the lasing spectra will be modulated.The lasing spectrum undergoes a Burstein-Moss(BM)effect-induced blueshift and an electron-hole plasma(EHP)effect-induced redshift.
基金National Natural Science Foundation of China(T2188101)。
文摘Among the synthesis techniques for graphene,chemical vapor deposition(CVD)enables the direct growth of graphene films on insulating substrates.Its advantages include uniform coverage,high quality,scalability,and compatibility with industrial processes.Graphene is chemically inert and has a zero-bandgap which poses a problem for its use as a functional layer,and nitrogen doping has become an important way to overcome this.Post-plasma treatment has been explored for the synthesis of nitrogen-doped graphene,but the procedures are intricate and not suitable for large-scale production.We report the direct synthesis of nitrogen-doped graphene on a 4-inch sapphire wafer by ethanol-assisted CVD employing pyridine as the carbon feedstock,where the nitrogen comes from the pyridine and the hydroxyl group in ethanol improves the quality of the graphene produced.Additionally,the types of nitrogen dopant produced and their effects on III-nitride epitaxy were also investigated,resulting in the successful illumination of LED devices.This work presents an effective synthesis strategy for the preparation of nitrogen-doped graphene,and provides a foundation for designing graphene functional layers in optoelectronic devices.
文摘A new type of 785 nm semiconductor laser device has been proposed.The thin cladding and mode expansion layer structure incorporated into the epitaxy on the p-side significantly impacts the regulation of grating etching depth.Thinning of the p-side waveguide layer makes the light field bias to the n-side cladding layer.By coordinating the confinement effect of the cladding layer,the light confinement factor on the p-side is regulated.On the other hand,the introduction of a mode expansion layer facilitates the expansion of the mode profile on the p side cladding layer.Both these factors contribute positively to reducing the grating etching depth.Compared to the reported epitaxial structures of symmetric waveguides,the new structure significantly reduces the etching depth of the grating while ensuring adequate reflection intensity and maintaining resonance.Moreover,to improve the output performance of the device,the new epitaxial structure has been optimized.Based on the traditional epitaxial structure,an energy release layer and an electron blocking layer are added to improve the electronic recombination efficiency.This improved structure has an output performance comparable to that of a symmetric waveguide,despite being able to have a smaller gain area.
文摘Epitaxy is usually used to produce high quality crystals with ato-mic perfection. Up to now, many semiconductor crystals of functional materials could be obtained by epitaxial growth techniques, such as molecular beam epitaxy, chemical vapor deposition, and liquid-phase epitaxy. However, these techniques are expensive, sophisticated, and not compatible with large area production. For solution-based deposition of epitaxial films such as hydrothermal processing [1], chemical bath deposition [2-3], and electrodeposition [4-5], specific conditions such as high temperature and pressure, or conducting substrates are commonly needed. Since single crystal epitaxial films have superior electronic and optical properties compared to amorphous and polycrystalline films due to absence of high-angle grain boundaries, searching for simple, rapid and inexpensive technique to grow epitaxial films is highly desired.
基金supported by the National Key R&D Program of China(2023YFA1610100).
文摘The Dzyaloshinskii‒Moriya interaction(DMI)at the interface of nonferromagnetic/ferromagnetic heterostructure films can induce the formation of chiral magnetic structures such as skyrmions,leading to the topological Hall effect(THE).Here,we report the first growth of high-quality La_(0.67)Sr_(0.33)MnO_(3)/Tb_(2)Ti_(2)O_(7)(LSMO/TTO)heterostructure films on single-crystal yttria-stabilized zirconia(111)substrates via laser molecular beam epitaxy.Electrical transport measurements reveal two key findings:(ⅰ)The anomalous Hall effect(AHE)of the LSMO/TTO heterostructure exhibits sign reversal within 50-100 K,and(ⅱ)a distinct hump signal emerges at low temperatures,differing from that of pure LSMO films.This hump signal weakens with increasing temperature,which is consistent with the characteristics of the THE.We propose that the THE-like signal originates from the LSMO lattice distortion induced by epitaxial growth on TTO,which breaks centrosymmetry and triggers DMI.Furthermore,the spin‒orbit coupling of Tb3+4f electrons likely generates interfacial spin currents,providing a driving force for the observed THE.
