Two-dimensional(2D)transition metal dichalcogenides(TMDs)have garnered widespread interest in the scientific community and industry for their exceptional physical and chemistry properties,and great potential for appli...Two-dimensional(2D)transition metal dichalcogenides(TMDs)have garnered widespread interest in the scientific community and industry for their exceptional physical and chemistry properties,and great potential for applications in diverse fields including(opto)electronics,electrocatalysis,and energy storage.Chemical vapor deposition(CVD)is one of the most compelling growth methods for the scalable growth of high-quality 2D TMDs.However,the conventional CVD process for synthesis of 2D TMDs still encounters significant challenges,primarily attributed to the high melting point of precursor powders,and achieving a uniform distribution of precursor atmosphere on the substrate to obtain controllable smaple domains is difficult.The spin-coating precursor mediated chemical vapor deposition(SCVD)strategy provides refinement over traditional methods by eliminating the use of solid precursors and ensuring a more clean and uniform distribution of the growth material on the substrate.Additionally,the SCVD process allows fine-tuning of material thickness and purity by manipulating solution composition,concentration,and the spin coating process.This Review presents a comprehensive summary of recent advances in controllable growth of 2D TMDs with a SCVD strategy.First,a series of various liquid precursors,additives,source supply methods,and substrate engineering strategies for preparing atomically thin TMDs by SCVD are introduced.Then,2D TMDs heterostructures and novel doped TMDs fabricated through the SCVD method are discussed.Finally,the current challenges and perspectives to synthesize 2D TMDs using SCVD are discussed.展开更多
Omnidirectional photodetectors attract enormous attention due to their prominent roles in optical tracking systems and omnidirectional cameras.However,it is still a challenge for the construction of high-performance o...Omnidirectional photodetectors attract enormous attention due to their prominent roles in optical tracking systems and omnidirectional cameras.However,it is still a challenge for the construction of high-performance omnidirectional photodetectors where the incident light can be effectively absorbed in multiple directions and the photo-generated carriers can be effectively collected.Here,a high-performance omnidirectional self-powered photodetector based on the CsSnBr_(3)/indium tin oxide(ITO)heterostructure film was designed and demonstrated.The as-fabricated photodetector exhibited an excellent self-powered photodetection performance,showing responsivity and detectivity up to 35.1 mA/W and 1.82×10^(10) Jones,respectively,along with the smart rise/decay response time of 4 ms/9 ms.Benefitting from the excellent photoelectric properties of the CsSnBr_(3) film as well as the ability of the CsSnBr_(3)/ITO heterostructure to efficiently separate and collect photo-generated carriers,the as-fabricated photodetector also exhibited an excellent omnidirectional self-powered photodetection performance.All the results have certified that this work finds an efficient way to realize high-performance omnidirectional self-powered photodetectors.展开更多
The fabrication of heterostructures of two-dimensional semiconductors with specific bandgaps is an important approach to realizing the full potential of these materials in electronic and optoelectronic devices. Severa...The fabrication of heterostructures of two-dimensional semiconductors with specific bandgaps is an important approach to realizing the full potential of these materials in electronic and optoelectronic devices. Several groups have recently reported the direct growth of lateral and vertical heterostructures based on monolayers of typical semiconducting transition metal dichalcogenides （TMDCs） such as WSe2, MoSe2, WS2, and MoS2. Here, we demonstrate the single-step direct growth of lateral and vertical heterostructures based on bandgap-tunable Mo1-xWxS2 alloy monolayers by the sulfurization of patterned thin films of WO3 and MoO3. These patterned films are capable of generating a wide variety of concentration gradients by the diffusion of transition metals during the crystal growth phase. Under high temperatures, this leads to the formation of monolayer crystals of Mo1-xWxS2 alloys with various compositions and bandgaps, depending on the positions of the crystals on the substrates. Heterostructures of these alloys are obtained through stepwise changes in the ratio of W/Mo within a single domain during low-temperature growth. The stabilization of the monolayer Mo1-xWxS2 alloys, which often degrade even under gentle conditions, was accomplished by coating the alloys with other monolayers. The present findings demonstrate an efficient means of both studying and optimizing the optical and electrical properties of TMDC-based heterostructures to allow use of the materials in future device applications.展开更多
Thermoelectric devices enable direct conversion between thermal and electrical energy.Recent studies have indicated that the thin film/substrate heterostructure is effective in achieving high thermoelectric performanc...Thermoelectric devices enable direct conversion between thermal and electrical energy.Recent studies have indicated that the thin film/substrate heterostructure is effective in achieving high thermoelectric performance via decoupling the Seebeck coefficient and electrical conductivity otherwise adversely inter-dependent in homogenous bulk materials.However,the mechanism underlying the thin film/substrate heterostructure thermoelectricity remains unclear.In addition,the power output of the thin film/substrate heterostructure is limited to the nanowatt scale to date,falling short of the practical application requirement.Here,we fabricated the CrN/SrTiO_(3-x) heterostructures with high thermoelectric output power and outstanding thermal stability.By varying the CrN film thickness and the reduction degree of CrN/SrTiO_(3-x) substrate,the optimized power output and the power density have respectively reached 276μWand 10^(8) mW/cm^(2) for the 30 nm CrN film on a highly reduced surface of CrN/SrTiO_(3-x) under a temperature difference of 300 K.The performance enhancement is attributed to the CrN/CrN/SrTiO_(3-x) heterointerface,corroborated by the band bending as revealed by the scanning Kelvin probe microscopy.These results will stimulate further research efforts towards interface thermoelectrics.展开更多
A heterostructure composed of a Bi2Fe4O9 film and an n−type Si substrate is fabricated.The characteristics of leakage current density versus electric field are investigated and the leakage current density is about 6&#...A heterostructure composed of a Bi2Fe4O9 film and an n−type Si substrate is fabricated.The characteristics of leakage current density versus electric field are investigated and the leakage current density is about 6×10^(−6) A/cm^(2) at an electric field of 200 kV/cm at 300 K.A strong photovoltaic effect is observed when the heterostructure is exposed to a laser pulse with a wavelength of 532 nm and a power of 6 mW/mm^(2).It is found that the peak photovoltages initially increase with decreasing temperature,followed by a decrease at T<210 K.These results reveal that the heterostructure is a promising candidate for photovoltaic devices that are compatible with Si integrated circuits.展开更多
SrTiO3 films with different cation concentration were deposited on Si（001） substrates by oxide molecular beam epitaxy. An amorphous layer was observed at the interface whose thickness depends on the oxygen pressure ...SrTiO3 films with different cation concentration were deposited on Si（001） substrates by oxide molecular beam epitaxy. An amorphous layer was observed at the interface whose thickness depends on the oxygen pressure and the substrate temperature during growth. Although lowering the oxygen vacancy concentration in SrTiO3 led to better insulating performance as indi- cated by the lowered leakage current density of the heterostructure, the dielectric performance was deteriorated because of the thickened interracial layer that dominated the capacitance of SrTiO3/Si heterostructure. Instead of adjusting the oxygen vacan- cy concentration, we propose that controlling the film cation concentration is an effective way to tune the dielectric and insu- lating properties of SrTiO3/Si at the same time.展开更多
The scope of the study is the spectra of low-temperature (T = 2K) photoluminescence of a p-CdTe/n-CdS film heterostructure comprising a monolayer of CdTe microcrystals, where a single microcrystalline particle is typi...The scope of the study is the spectra of low-temperature (T = 2K) photoluminescence of a p-CdTe/n-CdS film heterostructure comprising a monolayer of CdTe microcrystals, where a single microcrystalline particle is typically one micron in size. Focus is made on the dominant band of “super-hot” emission appearing in the spectral region located in energy above the fundamental absorption edge of a CdTe bulk crystal. A theoretical model has been developed that assumes the existence of a space-charge layer inside a microcrystal, which leads to the formation of a triangular potential well for an electron near the surface. The anomalous emission band arises as a result of the optical transitions of electrons from near-surface levels of spatial quantization to valence band states.展开更多
Thin film light-emitting diodes with organic/inorganic heterostructure in which ZnO:Zn layer was used as electron transporting and hole blocking layer, PDDOPV, Poly(2,5- Didodecyloxy-1,4 Phenylenevinylene ) was used a...Thin film light-emitting diodes with organic/inorganic heterostructure in which ZnO:Zn layer was used as electron transporting and hole blocking layer, PDDOPV, Poly(2,5- Didodecyloxy-1,4 Phenylenevinylene ) was used as hole transport and emission layer have been successfully prepared. Comparing to single layer device, the luminescent efficiency of bilayer device is improved about twenty-six times, the emission spectrum’s peak wavelength shifts to short wavelength, the half width at full maximum (HWFM) widens. The improvement of luminescent efficiency is due to the insertion of ZnO:Zn layer.展开更多
TiO2 rutile/anatase heterostructure thin films with varying rutile thickness have been in-situ synthesized via DC magnetron sputtering with Ar gas at room temperature. The crystal texture, surface morphology, energy g...TiO2 rutile/anatase heterostructure thin films with varying rutile thickness have been in-situ synthesized via DC magnetron sputtering with Ar gas at room temperature. The crystal texture, surface morphology, energy gap and optical properties of the films have been investigated by X-ray diffraction meter, grazing incidence X-ray diffraction meter, Raman spectroscopy, scanning electron microscopy, and UV–visible spectrophotometer, which indicates that the rutile/anatase heterostructure films are successfully fabricated. The further degradation experiments display that the photocatalytic activity can be dramatically affected by the thickness of the outmost rutile layer and the 100 nm thickness exhibits the best performance in all of the TiO2 thin films. With the increase of the outmost rutile layer, the optical band gap of TiO2 film displays a systematic decrease slightly. However,the change in photocatalytic activity does not coincide with that in the band gap. The photoresponse and electrochemical properties of the thin films have been characterized to understand the mechanism of the varied photocatalytic activity.展开更多
基金We acknowledge the support from the National Key R&D Program of the Ministry of Science and Technology of China(No.2022YFA1203801)the National Natural Science Foundation of China(grant numbers 51991340,51991343,52221001,62205055)+1 种基金the Hunan Key R&D Program Project(No.2022GK2005)Natural Science Foundation of Jiangsu Province(BK20220860).
文摘Two-dimensional(2D)transition metal dichalcogenides(TMDs)have garnered widespread interest in the scientific community and industry for their exceptional physical and chemistry properties,and great potential for applications in diverse fields including(opto)electronics,electrocatalysis,and energy storage.Chemical vapor deposition(CVD)is one of the most compelling growth methods for the scalable growth of high-quality 2D TMDs.However,the conventional CVD process for synthesis of 2D TMDs still encounters significant challenges,primarily attributed to the high melting point of precursor powders,and achieving a uniform distribution of precursor atmosphere on the substrate to obtain controllable smaple domains is difficult.The spin-coating precursor mediated chemical vapor deposition(SCVD)strategy provides refinement over traditional methods by eliminating the use of solid precursors and ensuring a more clean and uniform distribution of the growth material on the substrate.Additionally,the SCVD process allows fine-tuning of material thickness and purity by manipulating solution composition,concentration,and the spin coating process.This Review presents a comprehensive summary of recent advances in controllable growth of 2D TMDs with a SCVD strategy.First,a series of various liquid precursors,additives,source supply methods,and substrate engineering strategies for preparing atomically thin TMDs by SCVD are introduced.Then,2D TMDs heterostructures and novel doped TMDs fabricated through the SCVD method are discussed.Finally,the current challenges and perspectives to synthesize 2D TMDs using SCVD are discussed.
基金supported by the National Key R&D Program of China under Grant No.2017YFA0305500National Natural Science Foundation of China under Grant No.61904096,Taishan Scholars Program of Shandong Province under Grant No.tsqn201812006+2 种基金Natural Science Foundation of Shandong Province under Grants No.ZR2022JQ05 and No.ZR2022QF025Shandong University Multidisciplinary Research and Innovation Team of Young Scholars under Grant No.2020QNQT015“Outstanding Youth Scholar and Qilu Young Scholar”Programs of Shandong University.
文摘Omnidirectional photodetectors attract enormous attention due to their prominent roles in optical tracking systems and omnidirectional cameras.However,it is still a challenge for the construction of high-performance omnidirectional photodetectors where the incident light can be effectively absorbed in multiple directions and the photo-generated carriers can be effectively collected.Here,a high-performance omnidirectional self-powered photodetector based on the CsSnBr_(3)/indium tin oxide(ITO)heterostructure film was designed and demonstrated.The as-fabricated photodetector exhibited an excellent self-powered photodetection performance,showing responsivity and detectivity up to 35.1 mA/W and 1.82×10^(10) Jones,respectively,along with the smart rise/decay response time of 4 ms/9 ms.Benefitting from the excellent photoelectric properties of the CsSnBr_(3) film as well as the ability of the CsSnBr_(3)/ITO heterostructure to efficiently separate and collect photo-generated carriers,the as-fabricated photodetector also exhibited an excellent omnidirectional self-powered photodetection performance.All the results have certified that this work finds an efficient way to realize high-performance omnidirectional self-powered photodetectors.
文摘The fabrication of heterostructures of two-dimensional semiconductors with specific bandgaps is an important approach to realizing the full potential of these materials in electronic and optoelectronic devices. Several groups have recently reported the direct growth of lateral and vertical heterostructures based on monolayers of typical semiconducting transition metal dichalcogenides （TMDCs） such as WSe2, MoSe2, WS2, and MoS2. Here, we demonstrate the single-step direct growth of lateral and vertical heterostructures based on bandgap-tunable Mo1-xWxS2 alloy monolayers by the sulfurization of patterned thin films of WO3 and MoO3. These patterned films are capable of generating a wide variety of concentration gradients by the diffusion of transition metals during the crystal growth phase. Under high temperatures, this leads to the formation of monolayer crystals of Mo1-xWxS2 alloys with various compositions and bandgaps, depending on the positions of the crystals on the substrates. Heterostructures of these alloys are obtained through stepwise changes in the ratio of W/Mo within a single domain during low-temperature growth. The stabilization of the monolayer Mo1-xWxS2 alloys, which often degrade even under gentle conditions, was accomplished by coating the alloys with other monolayers. The present findings demonstrate an efficient means of both studying and optimizing the optical and electrical properties of TMDC-based heterostructures to allow use of the materials in future device applications.
基金supported by Liaoning Revitalization Talents Program (No. XLYC1807209)Dalian Institute of Chemical Physics (DICP I202037)the National Natural Science Foundation of China (Grant Nos. 21625304, 22022205).
文摘Thermoelectric devices enable direct conversion between thermal and electrical energy.Recent studies have indicated that the thin film/substrate heterostructure is effective in achieving high thermoelectric performance via decoupling the Seebeck coefficient and electrical conductivity otherwise adversely inter-dependent in homogenous bulk materials.However,the mechanism underlying the thin film/substrate heterostructure thermoelectricity remains unclear.In addition,the power output of the thin film/substrate heterostructure is limited to the nanowatt scale to date,falling short of the practical application requirement.Here,we fabricated the CrN/SrTiO_(3-x) heterostructures with high thermoelectric output power and outstanding thermal stability.By varying the CrN film thickness and the reduction degree of CrN/SrTiO_(3-x) substrate,the optimized power output and the power density have respectively reached 276μWand 10^(8) mW/cm^(2) for the 30 nm CrN film on a highly reduced surface of CrN/SrTiO_(3-x) under a temperature difference of 300 K.The performance enhancement is attributed to the CrN/CrN/SrTiO_(3-x) heterointerface,corroborated by the band bending as revealed by the scanning Kelvin probe microscopy.These results will stimulate further research efforts towards interface thermoelectrics.
基金by the National Natural Science Foundation of China under Grant Nos 61078057 and 50702046,NPU Foundation for Fundamental Research under Grant Nos NPU-FFR-JC200821 and JC201048,and NWPU Aoxiang Star Project.
文摘A heterostructure composed of a Bi2Fe4O9 film and an n−type Si substrate is fabricated.The characteristics of leakage current density versus electric field are investigated and the leakage current density is about 6×10^(−6) A/cm^(2) at an electric field of 200 kV/cm at 300 K.A strong photovoltaic effect is observed when the heterostructure is exposed to a laser pulse with a wavelength of 532 nm and a power of 6 mW/mm^(2).It is found that the peak photovoltages initially increase with decreasing temperature,followed by a decrease at T<210 K.These results reveal that the heterostructure is a promising candidate for photovoltaic devices that are compatible with Si integrated circuits.
基金supported by the National Basic Research Program of China(Grant No.2012CB921700)the National Natural Science Foundation of China(Grant No.11225422)the US Natural Science Foundation(Grant No.DMR-1106070)
文摘SrTiO3 films with different cation concentration were deposited on Si（001） substrates by oxide molecular beam epitaxy. An amorphous layer was observed at the interface whose thickness depends on the oxygen pressure and the substrate temperature during growth. Although lowering the oxygen vacancy concentration in SrTiO3 led to better insulating performance as indi- cated by the lowered leakage current density of the heterostructure, the dielectric performance was deteriorated because of the thickened interracial layer that dominated the capacitance of SrTiO3/Si heterostructure. Instead of adjusting the oxygen vacan- cy concentration, we propose that controlling the film cation concentration is an effective way to tune the dielectric and insu- lating properties of SrTiO3/Si at the same time.
文摘The scope of the study is the spectra of low-temperature (T = 2K) photoluminescence of a p-CdTe/n-CdS film heterostructure comprising a monolayer of CdTe microcrystals, where a single microcrystalline particle is typically one micron in size. Focus is made on the dominant band of “super-hot” emission appearing in the spectral region located in energy above the fundamental absorption edge of a CdTe bulk crystal. A theoretical model has been developed that assumes the existence of a space-charge layer inside a microcrystal, which leads to the formation of a triangular potential well for an electron near the surface. The anomalous emission band arises as a result of the optical transitions of electrons from near-surface levels of spatial quantization to valence band states.
文摘Thin film light-emitting diodes with organic/inorganic heterostructure in which ZnO:Zn layer was used as electron transporting and hole blocking layer, PDDOPV, Poly(2,5- Didodecyloxy-1,4 Phenylenevinylene ) was used as hole transport and emission layer have been successfully prepared. Comparing to single layer device, the luminescent efficiency of bilayer device is improved about twenty-six times, the emission spectrum’s peak wavelength shifts to short wavelength, the half width at full maximum (HWFM) widens. The improvement of luminescent efficiency is due to the insertion of ZnO:Zn layer.
基金supported by the National Natural Science Foundation of China (Nos. 21377044 and 21573085)the Key Project of Natural Science Foundation of Hubei Province (No. 2015CFA037)
文摘TiO2 rutile/anatase heterostructure thin films with varying rutile thickness have been in-situ synthesized via DC magnetron sputtering with Ar gas at room temperature. The crystal texture, surface morphology, energy gap and optical properties of the films have been investigated by X-ray diffraction meter, grazing incidence X-ray diffraction meter, Raman spectroscopy, scanning electron microscopy, and UV–visible spectrophotometer, which indicates that the rutile/anatase heterostructure films are successfully fabricated. The further degradation experiments display that the photocatalytic activity can be dramatically affected by the thickness of the outmost rutile layer and the 100 nm thickness exhibits the best performance in all of the TiO2 thin films. With the increase of the outmost rutile layer, the optical band gap of TiO2 film displays a systematic decrease slightly. However,the change in photocatalytic activity does not coincide with that in the band gap. The photoresponse and electrochemical properties of the thin films have been characterized to understand the mechanism of the varied photocatalytic activity.
