Recently,with the rapid development of chemical vapor deposition(CVD)technology,large area free-standing CVD diamond films have been produced successfully.However,the coarse grain size on the surface and the non-unifo...Recently,with the rapid development of chemical vapor deposition(CVD)technology,large area free-standing CVD diamond films have been produced successfully.However,the coarse grain size on the surface and the non-uniform thickness of unprocessed CVD diamond films make it difficult to meet the application requirement.The current study evaluates several existing polishing methods for CVD diamond films,including mechanical polishing,chemical mechanical polishing and tribochemical polishing technology.展开更多
Free-standing diamond films, deposited using DC Arc Plasma Jet CVD method onto graphite substrates with titanium interlayers, have been investigated. The Ti interlayers were deposited by arc ion plating equipments. Th...Free-standing diamond films, deposited using DC Arc Plasma Jet CVD method onto graphite substrates with titanium interlayers, have been investigated. The Ti interlayers were deposited by arc ion plating equipments. The thickness, morphology and composite phase of Ti interlayers were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The titanium carbide (TiC) was detected in both sides of the interlayers, which played an important role with respect to reasonable adhesion with film and diamond nucleation. The semi-translucent diamond films were characterized by SEM and Raman spectrum. The sharp diamond peak with low intensity of amorphous carbon shows that diamond films have very high quality. The overall results suggest that plating Ti interlayer on graphite substrate is an effective way to obtain optical grade free-standing diamond films.展开更多
Free-standing diamond films have been successfully deposited on stainless steel substrates using microwave plasma-assisted chemical vapor deposition. Although iron, which is the main element of stainless steel, is kno...Free-standing diamond films have been successfully deposited on stainless steel substrates using microwave plasma-assisted chemical vapor deposition. Although iron, which is the main element of stainless steel, is known to inhibit the nucleation of diamond and enhance the formation of graphite, we were able to grow relatively thick films (-1.2 mm). The films were easily detachable from the substrates. The poor adhesion made it possible to obtain free-standing diamond films without chemical etching. Raman spectroscopy showed the 1332 cm^-1 characteristic Raman peak of diamond and the 1580 cm^-1, 1350 cm^-1 bands of graphite on the growth surface and backside of the films, respectively. By energy dispersive X-ray spectroscopy it was only possible to detect iron on the back of the films, but not on the surface. The role of iron in the film growth is discussed.展开更多
Free-standing diamond films were prepared by hot filament chemical vapor deposition (HFCVD) method under different conditions. Inter-digital transducers (IDTs) were formed on the nucleation sides of free-standing diam...Free-standing diamond films were prepared by hot filament chemical vapor deposition (HFCVD) method under different conditions. Inter-digital transducers (IDTs) were formed on the nucleation sides of free-standing diamond films by photolithography technique. Then piezoelectric ZnO films were deposited by radio-frequency(RF) reactive magnetron sputtering to obtain the ZnO/diamond film structures. Surface morphologies of the nucleation sides and the IDTs were characterized by means of scanning electron microscopy (SEM), atomic force microscope (AFM) and optical microscopy. The results indicate that the surfaces of nucleation sides are very smooth and the IDTs are of high quality without discontinuity and short circuit phenomenon. Raman spectra show the sharp diamond feature peak at about 1 334 cm?1 and the small amount of non-diamond carbon in the nucleation side. X-ray diffraction (XRD) patterns of the structure of ZnO/diamond films show a strong diffraction peak of ZnO (002), which indicates that as-sputtered ZnO films are highly c-axis oriented.展开更多
Highly c-axis-oriented ZnO films were deposited successfully on the nucleation sides of free-standing diamond (FD) films by the direct current (DC) magnetron sputtering method. The effect of the sputtering paramet...Highly c-axis-oriented ZnO films were deposited successfully on the nucleation sides of free-standing diamond (FD) films by the direct current (DC) magnetron sputtering method. The effect of the sputtering parameters, such as power, gas pressure and sputtering plasma composition of Ar-to-O2, on the properties of ZnO thin films was investigated in detail. X-ray diffraction (XRD) measurements showed that, at a sputtering power of 200 W, gas pressure of 0.5 Pa and an Ar-to- O2 composition of 1:1, a higher intensity of the (002) diffraction peak and a narrower full width at half maximum (FWHM) were detected which meant high c-axis orientation and high quality of the ZnO films. To improve the quality of the ZnO film, a thin ZnO layer was pre-grown as a homo-buffer layer. XRD measurements showed that this buffer layer had a beneficial effect on the structural and morphological properties of the post-grown ZnO film.展开更多
Blue-green electroluminescence has been observed in free-standing diamond films which were deposited by microwave plasma assisted CVD on silicon substrates.The electroluminescence device is driven by a 60 Hz power sup...Blue-green electroluminescence has been observed in free-standing diamond films which were deposited by microwave plasma assisted CVD on silicon substrates.The electroluminescence device is driven by a 60 Hz power supply.The threshold voltage was about 112 V peak-to-peak.The electroluminescence spectrum at room temperature,showed a blue-green band with the peak centered at 485nm suggesting band A type emission.Electroluminescence was also observed at 77K.展开更多
An insulate to metal transition was investigated based on the measurements of the dependence of the conductivity, activation energy on the protonation state of polyaniline (PANI). An isotropy in conductivity for stret...An insulate to metal transition was investigated based on the measurements of the dependence of the conductivity, activation energy on the protonation state of polyaniline (PANI). An isotropy in conductivity for stretched salt form of PANI was observed.For salt film of PANI, the Ⅰ-Ⅴ curve obeys Ohm's law, which shows a typical metal behavior, however, for base film or film with low protonation state, it can be explained by Space Charge Limited Current (SCLC). It is also found that the Ⅰ-Ⅴ curve of base film of PANI is independent of the work function of electrodes and the polymerization temperature.展开更多
Under optimal conditions free-standing high quality diamond films were prepared by DC arc plasma jet CVD method at a growth rate of 7-10 Pm/h. Surface and cross section morphologies of the diamond films were observed ...Under optimal conditions free-standing high quality diamond films were prepared by DC arc plasma jet CVD method at a growth rate of 7-10 Pm/h. Surface and cross section morphologies of the diamond films were observed by SEM. Raman spectrometer wasused to characterize the quality of diamond films. The IR transmittivity measured by IR spectrometer is close to the theoretical value ofabout 71% in the far infrared band. The thermal conductivity measured by photothermal deflection exceeds 18 W/cm' K. <l 10> is thepreferential growth orientation of the films detected by X-ray diffractometer. As s result, the extremely high temperature of DC arc plasma jet can produce supersaturated atomic hydrogen, which played an important role in the process for the deposition of high quality diamond films.展开更多
Flexible electronic devices have attracted much attention due to their practical and commercial value. Integration of thin films with soft substrate is an effective way to fabricate flexible electronic devices. Ga_2O_...Flexible electronic devices have attracted much attention due to their practical and commercial value. Integration of thin films with soft substrate is an effective way to fabricate flexible electronic devices. Ga_2O_3 thin films deposited directly on soft substrates would be amorphous mostly. However, the thickness of the thin film obtained by mechanical exfoliation method is difficult to control and the edge of the film is fragile and easy to be damaged. In this work, we fabricated free-standing Ga_2O_3 thin films using the water-soluble perovskite Sr_3Al_2O_6 as a sacrificial buffer layer. The obtained Ga_2O_3 thin films were polycrystalline. The thickness and dimension of the films were controllable. A flexible Ga_2O_3solar-blind UV photodetector was fabricated by transferring the free-standing Ga_2O_3 film on a flexible polyethylene terephthalate substrate. The results displayed that the photoelectric performances of the flexible Ga_2O_3 photodetector were not sensitive to bending of the device. The free-standing Ga_2O_3 thin films synthesized through the method described here can be transferred to any substrates or integrated with other thin films to fabricate electronic devices.展开更多
The structure characteristic and electric performance of ZnO film deposited on nucleation side of free-standing diamond substrates under different heating temperatures (Th) of substrate and working pressures (p) were ...The structure characteristic and electric performance of ZnO film deposited on nucleation side of free-standing diamond substrates under different heating temperatures (Th) of substrate and working pressures (p) were studied. The structure of the ZnO films tested by X-ray diffraction shows that ZnO film of high c-axis orientation is deposited on the nucleation side of free-standing diamond substrate which is extremely smooth when Th=250 ℃ and p=0.4 Pa. After annealing at 480 ℃ in N2 atmosphere, the SEM and the AFM analyses demonstrate that the c-axis orientation of ZnO film is obviously enhanced. The resistivity of ZnO films also increases up to 8×105 ■·cm which is observed by I?V test.展开更多
During the growth of the hot filament chemical vapor deposition (HFCVD) diamond films, numerical simulations in a 2-D mathematical model were employed to investigate the influence of various deposition parameters on...During the growth of the hot filament chemical vapor deposition (HFCVD) diamond films, numerical simulations in a 2-D mathematical model were employed to investigate the influence of various deposition parameters on the gas physical parameters, including the temperature, velocity and volume density of gas. It was found that, even in the case of optimized deposition parameters, the space distributions of gas parameters were heterogeneous due primarily to the thermal blockage come from the hot filaments and cryogenic pump effect arisen from the cold reactor wall. The distribution of volume density agreed well with the thermal round-flow phenomenon, one of the key obstacles to obtaining high growth rate in HFCVD process. In virtue of isothermal boundary with high temperature or adiabatic boundary condition of reactor wall, however, the thermal roundflow was profoundly reduced and as a consequence, the uniformity of gas physical parameters was considerably improved, as identified by the experimental films growth.展开更多
Selective deposition of diamond film on patterned Si (100) substrates has been achieved by using microwave plasma chemical vapor deposition (MPCVD) method. The films have been characterized by scanning electron micr...Selective deposition of diamond film on patterned Si (100) substrates has been achieved by using microwave plasma chemical vapor deposition (MPCVD) method. The films have been characterized by scanning electron microscope (SEM) and Raman spectrum. The influence of substrate temperature on the nucleation behavior of diamond was discussed in detail and the optimized deposition condition has been obtained.展开更多
The etching technique using Ce is a convenient and fast method for polishing and shaping diamond films. In this study, the influence of polishing parameters such as polishing temperature and time on the surface crysta...The etching technique using Ce is a convenient and fast method for polishing and shaping diamond films. In this study, the influence of polishing parameters such as polishing temperature and time on the surface crystallinity and phase composition of diamond films was thoroughly investigated via the analysis of Raman spectra such as FWHM and ID/IG. Moreover, the issue on the graphitization of diamond after polishing with Ce was further researched through the detailed study of the depth distribution of Raman data including FWHM and ID/IG, and a result completely different from the hot-iron metal polished ones was obtained. The results showed that polished diamond films had considerably higher diamond content than those before polishing, and not a bit of graphitization was found in the polished ones, owing to a higher solubility of carbon in rare earth metal Ce than that in transition metals, and the original crystallinity of the films polished with Ce did not deteriorate.展开更多
With the advantages of high deposition rate and large deposition area, polycrystalline diamond films prepared by direct current (DC) arc jet chemical vapor deposition (CVD) are considered to be one of the most pro...With the advantages of high deposition rate and large deposition area, polycrystalline diamond films prepared by direct current (DC) arc jet chemical vapor deposition (CVD) are considered to be one of the most promising materials for high-frequency and high-power electronic devices. In this paper, high-quality self-standing polycrystalline diamond films with the diameter of 100 mm were prepared by DC arc jet CVD, and then, the p-type surface conductive layer with the sheet carrier density of 10^11-10^13 cm-2 on the H-terminated diamond film was obtained by micro-wave hydrogen plasma treatment for 40 min. Ti/Au and Au films were deposited on the H-terminated diamond surface as the ohmic contact electrode, respectively, afterwards, they were treated by rapid vacuum annealing at different temperatures. The properties of these two types of ohmic contacts were investigated by measuring the specific contact resistance using the transmission line method (TLM). Due to the formation of Ti-related carbide at high temperature, the specific contact resistance of Ti/Au contact gradually decreases to 9.95 × 10^-5 Ω-cm2 as the temperature increases to 820℃. However, when the annealing temperature reaches 850℃, the ohmic contact for Ti/Au is degraded significantly due to the strong diffusion and reaction between Ti and Au. As for the as-deposited Au contact, it shows an ohmic contact. After annealing treatment at 550℃, low specific contact resistance was detected for Au contact, which is derived from the enhancement of interdiffusion between Au and diamond films.展开更多
Cu ion implantation and subsequent rapid annealing at 500℃ in N2 result in low surface resistivity of 1.611 ohm/sq with high mobility of 290 cm2 V-1S-1 for microcrystalline diamond (MCD) films. Its electrical field...Cu ion implantation and subsequent rapid annealing at 500℃ in N2 result in low surface resistivity of 1.611 ohm/sq with high mobility of 290 cm2 V-1S-1 for microcrystalline diamond (MCD) films. Its electrical field emission behavior can be turned on at Eo = 2.6 V/μm, attaining a current density of 19.5μA/cm2 at an applied field of 3.5 V/#m. Field emission scanning electron microscopy combined with Raman and x-ray photoelectron mi- croscopy reveal that the formation of Cu nanoparticles in MCD films can catalytically convert the less conducting disorder/a-C phases into graphitic phases and can provoke the formation of nanographite in the films, forming conduction channels for electron transportation.展开更多
Monte Carlo simulations are adopted to study the electron motion in the mixture of H2 and CH4 during diamond synthesis via Glow Plasma-assisted Chemical Vapor Deposition (GPCVD). The non-uniform electric field is used...Monte Carlo simulations are adopted to study the electron motion in the mixture of H2 and CH4 during diamond synthesis via Glow Plasma-assisted Chemical Vapor Deposition (GPCVD). The non-uniform electric field is used and the avalanche of electrons is taken into account in this simulation. The average energy distribution of electrons and the space distribution of effective species such as CH3, CH+3, CH+ and H at various gas pressures are given in this paper, and optimum experimental conditions are inferred from these results.展开更多
A free-standing diamond film with millimeter thickness prepared by DC arc plasma jet was thinned successively by mechanical grinding. The orientation and quality of the diamond films with different thicknesses were ch...A free-standing diamond film with millimeter thickness prepared by DC arc plasma jet was thinned successively by mechanical grinding. The orientation and quality of the diamond films with different thicknesses were characterized by X-ray diffraction and Raman spectroscopy, respectively. The results show a random grain-orientatinn distribution during the initial growth stage. As the film thickness increases, the preferred orientation of the diamond film changes from (111) to (220), due to the competitive growth mechanism. Twinning generated during the nucleation stage appears to stabilize the preferential growth along the 〈110〉 direction. The interplanar spacing of the (220) plane is enlarged as the film thickness increases, which is caused by the increase of non-diamond-phase carbon and impurities under the cyclic gas. In addition, the quality of the diamond film is barely degraded during the growth process. Furthermore, the peak shift demonstrates a significant inhomogeneity of stress along the film growth direction, which results from competitive growth.展开更多
Oxygen-doped diamond films are prepared by implanting various dose oxygen ions into the diamond films synthesized by hot filament chemical vapour deposition, and their electrical and structural properties are investig...Oxygen-doped diamond films are prepared by implanting various dose oxygen ions into the diamond films synthesized by hot filament chemical vapour deposition, and their electrical and structural properties are investigated. Hall effect measurements show that lower dose oxygen ion implantation is beneficial to preparing n-type diamonds. The carrier concentration increases with the dose increasing, indicating that oxygen ions supply electrons to the diamonds. The results of AES spectrum indicate that oxygen ions are doped into the diamond films, and the O-implanted depth is around 0.1μm. Raman spectrum measurements indicate that the lower dose oxygen ion implantation at 10^14 cm^-2 or 10^15 cm^-2 is favourable for producing less damaged O-doDed diamond films.展开更多
Microcrystalline diamond(MCD)films with different grain sizes ranging from 160 nm to 2200 nm are prepared by using a hot filament chemical vapor deposition(HFCVD)system,and the influences of grain size and structural ...Microcrystalline diamond(MCD)films with different grain sizes ranging from 160 nm to 2200 nm are prepared by using a hot filament chemical vapor deposition(HFCVD)system,and the influences of grain size and structural features on optical properties are investigated.The results show that the film with grain size in a range of 160 nm–310 nm exhibits a higher refractive index in a range of(2.77–2.92).With grain size increasing to 620±300 nm,the refractive index shows a value between 2.39 and 2.47,approaching to that of natural diamond(2.37–2.55),and a lower extinction coefficient value between 0.08 and 0.77.When the grain size increases to 2200 nm,the value of refractive index increases to a value between 2.66 and 2.81,and the extinction coefficient increases to a value in a range of 0.22–1.28.Visible Raman spectroscopy measurements show that all samples have distinct diamond peaks located in a range of 1331 cm-1–1333 cm-1,the content of diamond phase increases gradually as grain size increases,and the amount of trans-polyacetylene(TPA)content decreases.Meanwhile,the sp2 carbon clusters content and its full-width-at-half-maximum(FWHM)value are significantly reduced in MCD film with a grain size of 620 nm,which is beneficial to the improvement of the optical properties of the films.展开更多
A much larger amount of bonded hydrogen was found in thick nanocrystalline diamond (NCD) films produced by only adding 0.24% N2 into 4% CH4/H2 plasma, as compared to the high quality transparent microcrystalline dia...A much larger amount of bonded hydrogen was found in thick nanocrystalline diamond (NCD) films produced by only adding 0.24% N2 into 4% CH4/H2 plasma, as compared to the high quality transparent microcrystalline diamond (MCD) films, grown using the same growth parameters except for nitrogen. These experimental results clearly evidence that defect formation and impurity incorporation (for example, N and H) impeding diamond grain growth is the main formation mechanism of NCD upon nitrogen doping and strongly support the model proposed in the literature that nitrogen competes with CHx (x = 1, 2, 3) growth species for adsorption sites.展开更多
基金Science and technology plan project of Hebei Academy of Sciences(No.191408)Natural Science Foundation of Hebei Province(E2019302005)
文摘Recently,with the rapid development of chemical vapor deposition(CVD)technology,large area free-standing CVD diamond films have been produced successfully.However,the coarse grain size on the surface and the non-uniform thickness of unprocessed CVD diamond films make it difficult to meet the application requirement.The current study evaluates several existing polishing methods for CVD diamond films,including mechanical polishing,chemical mechanical polishing and tribochemical polishing technology.
基金financially supported by the Graduate Student Foundation of University of Science and Technology BeijingNational Natural Science Foundation of China
文摘Free-standing diamond films, deposited using DC Arc Plasma Jet CVD method onto graphite substrates with titanium interlayers, have been investigated. The Ti interlayers were deposited by arc ion plating equipments. The thickness, morphology and composite phase of Ti interlayers were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The titanium carbide (TiC) was detected in both sides of the interlayers, which played an important role with respect to reasonable adhesion with film and diamond nucleation. The semi-translucent diamond films were characterized by SEM and Raman spectrum. The sharp diamond peak with low intensity of amorphous carbon shows that diamond films have very high quality. The overall results suggest that plating Ti interlayer on graphite substrate is an effective way to obtain optical grade free-standing diamond films.
文摘Free-standing diamond films have been successfully deposited on stainless steel substrates using microwave plasma-assisted chemical vapor deposition. Although iron, which is the main element of stainless steel, is known to inhibit the nucleation of diamond and enhance the formation of graphite, we were able to grow relatively thick films (-1.2 mm). The films were easily detachable from the substrates. The poor adhesion made it possible to obtain free-standing diamond films without chemical etching. Raman spectroscopy showed the 1332 cm^-1 characteristic Raman peak of diamond and the 1580 cm^-1, 1350 cm^-1 bands of graphite on the growth surface and backside of the films, respectively. By energy dispersive X-ray spectroscopy it was only possible to detect iron on the back of the films, but not on the surface. The role of iron in the film growth is discussed.
基金Projects(60577040) supported by the National Natural Science Foundation of China Project(0404) supported by the Shanghai Foundation of Applied Materials Research and Development+1 种基金 Projects(0452nm051, 05nm05046) supported by the Nano-technology Project of Shanghai Project(T0101) supported by the Shanghai Leading Academic Disciplines
文摘Free-standing diamond films were prepared by hot filament chemical vapor deposition (HFCVD) method under different conditions. Inter-digital transducers (IDTs) were formed on the nucleation sides of free-standing diamond films by photolithography technique. Then piezoelectric ZnO films were deposited by radio-frequency(RF) reactive magnetron sputtering to obtain the ZnO/diamond film structures. Surface morphologies of the nucleation sides and the IDTs were characterized by means of scanning electron microscopy (SEM), atomic force microscope (AFM) and optical microscopy. The results indicate that the surfaces of nucleation sides are very smooth and the IDTs are of high quality without discontinuity and short circuit phenomenon. Raman spectra show the sharp diamond feature peak at about 1 334 cm?1 and the small amount of non-diamond carbon in the nucleation side. X-ray diffraction (XRD) patterns of the structure of ZnO/diamond films show a strong diffraction peak of ZnO (002), which indicates that as-sputtered ZnO films are highly c-axis oriented.
基金National Natural Science Foundation of China (Nos.60577040,60877017)Program for Changjiang Scholars,Innovative Research Team in University of China (No.IRT0739)+1 种基金Innovation Program of Shanghai Municipal Education Commission of China (08YZ04)Shanghai Leading Academic Disciplines of China (S30107)
文摘Highly c-axis-oriented ZnO films were deposited successfully on the nucleation sides of free-standing diamond (FD) films by the direct current (DC) magnetron sputtering method. The effect of the sputtering parameters, such as power, gas pressure and sputtering plasma composition of Ar-to-O2, on the properties of ZnO thin films was investigated in detail. X-ray diffraction (XRD) measurements showed that, at a sputtering power of 200 W, gas pressure of 0.5 Pa and an Ar-to- O2 composition of 1:1, a higher intensity of the (002) diffraction peak and a narrower full width at half maximum (FWHM) were detected which meant high c-axis orientation and high quality of the ZnO films. To improve the quality of the ZnO film, a thin ZnO layer was pre-grown as a homo-buffer layer. XRD measurements showed that this buffer layer had a beneficial effect on the structural and morphological properties of the post-grown ZnO film.
基金the National Natural Science Foundation of China,and the Natural Science Foundation of He'nan province.
文摘Blue-green electroluminescence has been observed in free-standing diamond films which were deposited by microwave plasma assisted CVD on silicon substrates.The electroluminescence device is driven by a 60 Hz power supply.The threshold voltage was about 112 V peak-to-peak.The electroluminescence spectrum at room temperature,showed a blue-green band with the peak centered at 485nm suggesting band A type emission.Electroluminescence was also observed at 77K.
文摘An insulate to metal transition was investigated based on the measurements of the dependence of the conductivity, activation energy on the protonation state of polyaniline (PANI). An isotropy in conductivity for stretched salt form of PANI was observed.For salt film of PANI, the Ⅰ-Ⅴ curve obeys Ohm's law, which shows a typical metal behavior, however, for base film or film with low protonation state, it can be explained by Space Charge Limited Current (SCLC). It is also found that the Ⅰ-Ⅴ curve of base film of PANI is independent of the work function of electrodes and the polymerization temperature.
文摘Under optimal conditions free-standing high quality diamond films were prepared by DC arc plasma jet CVD method at a growth rate of 7-10 Pm/h. Surface and cross section morphologies of the diamond films were observed by SEM. Raman spectrometer wasused to characterize the quality of diamond films. The IR transmittivity measured by IR spectrometer is close to the theoretical value ofabout 71% in the far infrared band. The thermal conductivity measured by photothermal deflection exceeds 18 W/cm' K. <l 10> is thepreferential growth orientation of the films detected by X-ray diffractometer. As s result, the extremely high temperature of DC arc plasma jet can produce supersaturated atomic hydrogen, which played an important role in the process for the deposition of high quality diamond films.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51572033,51572241,61774019,61704153,and 11404029)the Fund of State Key Laboratory of IPOC(BUPT)+1 种基金the Open Fund of IPOC(BUPT)Beijing Municipal Commission of Science and Technology,China(Grant No.SX2018-04)
文摘Flexible electronic devices have attracted much attention due to their practical and commercial value. Integration of thin films with soft substrate is an effective way to fabricate flexible electronic devices. Ga_2O_3 thin films deposited directly on soft substrates would be amorphous mostly. However, the thickness of the thin film obtained by mechanical exfoliation method is difficult to control and the edge of the film is fragile and easy to be damaged. In this work, we fabricated free-standing Ga_2O_3 thin films using the water-soluble perovskite Sr_3Al_2O_6 as a sacrificial buffer layer. The obtained Ga_2O_3 thin films were polycrystalline. The thickness and dimension of the films were controllable. A flexible Ga_2O_3solar-blind UV photodetector was fabricated by transferring the free-standing Ga_2O_3 film on a flexible polyethylene terephthalate substrate. The results displayed that the photoelectric performances of the flexible Ga_2O_3 photodetector were not sensitive to bending of the device. The free-standing Ga_2O_3 thin films synthesized through the method described here can be transferred to any substrates or integrated with other thin films to fabricate electronic devices.
基金Project (60577040) supported by the National Natural Science Foundation of China Project (0404) supported by the Shanghai Foundation of Applied Materials Research and Development+1 种基金 Projects(0452nm051, 05nm05046) supported by the Nano-technology Project of Shanghai Project (T0101) supported by the Shanghai Leading Academic Disciplines
文摘The structure characteristic and electric performance of ZnO film deposited on nucleation side of free-standing diamond substrates under different heating temperatures (Th) of substrate and working pressures (p) were studied. The structure of the ZnO films tested by X-ray diffraction shows that ZnO film of high c-axis orientation is deposited on the nucleation side of free-standing diamond substrate which is extremely smooth when Th=250 ℃ and p=0.4 Pa. After annealing at 480 ℃ in N2 atmosphere, the SEM and the AFM analyses demonstrate that the c-axis orientation of ZnO film is obviously enhanced. The resistivity of ZnO films also increases up to 8×105 ■·cm which is observed by I?V test.
基金This work was partially supported by the National Natural Science Foundation of China (NSFC) under Contract No. 59292800 the Science and Technology Committee of Liaoning Province.
文摘During the growth of the hot filament chemical vapor deposition (HFCVD) diamond films, numerical simulations in a 2-D mathematical model were employed to investigate the influence of various deposition parameters on the gas physical parameters, including the temperature, velocity and volume density of gas. It was found that, even in the case of optimized deposition parameters, the space distributions of gas parameters were heterogeneous due primarily to the thermal blockage come from the hot filaments and cryogenic pump effect arisen from the cold reactor wall. The distribution of volume density agreed well with the thermal round-flow phenomenon, one of the key obstacles to obtaining high growth rate in HFCVD process. In virtue of isothermal boundary with high temperature or adiabatic boundary condition of reactor wall, however, the thermal roundflow was profoundly reduced and as a consequence, the uniformity of gas physical parameters was considerably improved, as identified by the experimental films growth.
文摘Selective deposition of diamond film on patterned Si (100) substrates has been achieved by using microwave plasma chemical vapor deposition (MPCVD) method. The films have been characterized by scanning electron microscope (SEM) and Raman spectrum. The influence of substrate temperature on the nucleation behavior of diamond was discussed in detail and the optimized deposition condition has been obtained.
文摘The etching technique using Ce is a convenient and fast method for polishing and shaping diamond films. In this study, the influence of polishing parameters such as polishing temperature and time on the surface crystallinity and phase composition of diamond films was thoroughly investigated via the analysis of Raman spectra such as FWHM and ID/IG. Moreover, the issue on the graphitization of diamond after polishing with Ce was further researched through the detailed study of the depth distribution of Raman data including FWHM and ID/IG, and a result completely different from the hot-iron metal polished ones was obtained. The results showed that polished diamond films had considerably higher diamond content than those before polishing, and not a bit of graphitization was found in the polished ones, owing to a higher solubility of carbon in rare earth metal Ce than that in transition metals, and the original crystallinity of the films polished with Ce did not deteriorate.
基金financially supported by the National Natural Science Foundation of China (No. 51272024)the Ph.D. Programs Foundation of the Ministry of Education of China (No. 20110006110011)the Fundamental Research Funds for Central Universities (No. FRF-TP-13-035A)
文摘With the advantages of high deposition rate and large deposition area, polycrystalline diamond films prepared by direct current (DC) arc jet chemical vapor deposition (CVD) are considered to be one of the most promising materials for high-frequency and high-power electronic devices. In this paper, high-quality self-standing polycrystalline diamond films with the diameter of 100 mm were prepared by DC arc jet CVD, and then, the p-type surface conductive layer with the sheet carrier density of 10^11-10^13 cm-2 on the H-terminated diamond film was obtained by micro-wave hydrogen plasma treatment for 40 min. Ti/Au and Au films were deposited on the H-terminated diamond surface as the ohmic contact electrode, respectively, afterwards, they were treated by rapid vacuum annealing at different temperatures. The properties of these two types of ohmic contacts were investigated by measuring the specific contact resistance using the transmission line method (TLM). Due to the formation of Ti-related carbide at high temperature, the specific contact resistance of Ti/Au contact gradually decreases to 9.95 × 10^-5 Ω-cm2 as the temperature increases to 820℃. However, when the annealing temperature reaches 850℃, the ohmic contact for Ti/Au is degraded significantly due to the strong diffusion and reaction between Ti and Au. As for the as-deposited Au contact, it shows an ohmic contact. After annealing treatment at 550℃, low specific contact resistance was detected for Au contact, which is derived from the enhancement of interdiffusion between Au and diamond films.
基金Supported by the National Natural Science Foundation of China under Grant No 11405114the Natural Science Foundation of Shanxi Province under Grant No 2015021065
文摘Cu ion implantation and subsequent rapid annealing at 500℃ in N2 result in low surface resistivity of 1.611 ohm/sq with high mobility of 290 cm2 V-1S-1 for microcrystalline diamond (MCD) films. Its electrical field emission behavior can be turned on at Eo = 2.6 V/μm, attaining a current density of 19.5μA/cm2 at an applied field of 3.5 V/#m. Field emission scanning electron microscopy combined with Raman and x-ray photoelectron mi- croscopy reveal that the formation of Cu nanoparticles in MCD films can catalytically convert the less conducting disorder/a-C phases into graphitic phases and can provoke the formation of nanographite in the films, forming conduction channels for electron transportation.
基金This work was supported by Doctor Foundation of Hebei Education Committee Hebei Natural Science Foundation(599091 ) of China
文摘Monte Carlo simulations are adopted to study the electron motion in the mixture of H2 and CH4 during diamond synthesis via Glow Plasma-assisted Chemical Vapor Deposition (GPCVD). The non-uniform electric field is used and the avalanche of electrons is taken into account in this simulation. The average energy distribution of electrons and the space distribution of effective species such as CH3, CH+3, CH+ and H at various gas pressures are given in this paper, and optimum experimental conditions are inferred from these results.
基金financially supported by the National Natural Science Foundation of China (No. 51272024)the Ph.D. Programs Foundation of the Ministry of Education of China (No. 20110006110011)the Fundamental Research Funds for Central Universities of China (No. FRF-TP-13-035A)
文摘A free-standing diamond film with millimeter thickness prepared by DC arc plasma jet was thinned successively by mechanical grinding. The orientation and quality of the diamond films with different thicknesses were characterized by X-ray diffraction and Raman spectroscopy, respectively. The results show a random grain-orientatinn distribution during the initial growth stage. As the film thickness increases, the preferred orientation of the diamond film changes from (111) to (220), due to the competitive growth mechanism. Twinning generated during the nucleation stage appears to stabilize the preferential growth along the 〈110〉 direction. The interplanar spacing of the (220) plane is enlarged as the film thickness increases, which is caused by the increase of non-diamond-phase carbon and impurities under the cyclic gas. In addition, the quality of the diamond film is barely degraded during the growth process. Furthermore, the peak shift demonstrates a significant inhomogeneity of stress along the film growth direction, which results from competitive growth.
文摘Oxygen-doped diamond films are prepared by implanting various dose oxygen ions into the diamond films synthesized by hot filament chemical vapour deposition, and their electrical and structural properties are investigated. Hall effect measurements show that lower dose oxygen ion implantation is beneficial to preparing n-type diamonds. The carrier concentration increases with the dose increasing, indicating that oxygen ions supply electrons to the diamonds. The results of AES spectrum indicate that oxygen ions are doped into the diamond films, and the O-implanted depth is around 0.1μm. Raman spectrum measurements indicate that the lower dose oxygen ion implantation at 10^14 cm^-2 or 10^15 cm^-2 is favourable for producing less damaged O-doDed diamond films.
基金Project supported by the Key Project of the National Natural Science Foundation of China(Grant No.U1809210)the National Natural Science Foundation of China(Grant Nos.50972129 and 50602039)+4 种基金the International Science Technology Cooperation Program of China(Grant No.2014DFR51160)the National Key Research and Development Program of China(Grant No.2016YFE0133200)the European Union’s Horizon 2020 Research and Innovation Staff Exchange(RISE)Scheme(Grant No.734578)the Belt and Road International Cooperation Project from Key Research and Development Program of Zhejiang Province,China(Grant No.2018C04021)the Natural Science Foundation of Zhejiang Province,China(Grant Nos.LQ15A040004 and LY18E020013)
文摘Microcrystalline diamond(MCD)films with different grain sizes ranging from 160 nm to 2200 nm are prepared by using a hot filament chemical vapor deposition(HFCVD)system,and the influences of grain size and structural features on optical properties are investigated.The results show that the film with grain size in a range of 160 nm–310 nm exhibits a higher refractive index in a range of(2.77–2.92).With grain size increasing to 620±300 nm,the refractive index shows a value between 2.39 and 2.47,approaching to that of natural diamond(2.37–2.55),and a lower extinction coefficient value between 0.08 and 0.77.When the grain size increases to 2200 nm,the value of refractive index increases to a value between 2.66 and 2.81,and the extinction coefficient increases to a value in a range of 0.22–1.28.Visible Raman spectroscopy measurements show that all samples have distinct diamond peaks located in a range of 1331 cm-1–1333 cm-1,the content of diamond phase increases gradually as grain size increases,and the amount of trans-polyacetylene(TPA)content decreases.Meanwhile,the sp2 carbon clusters content and its full-width-at-half-maximum(FWHM)value are significantly reduced in MCD film with a grain size of 620 nm,which is beneficial to the improvement of the optical properties of the films.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10874021)Natural Science Foundation of Educational Department of Jiangsu Province of China (Grant No. 06kja43014)
文摘A much larger amount of bonded hydrogen was found in thick nanocrystalline diamond (NCD) films produced by only adding 0.24% N2 into 4% CH4/H2 plasma, as compared to the high quality transparent microcrystalline diamond (MCD) films, grown using the same growth parameters except for nitrogen. These experimental results clearly evidence that defect formation and impurity incorporation (for example, N and H) impeding diamond grain growth is the main formation mechanism of NCD upon nitrogen doping and strongly support the model proposed in the literature that nitrogen competes with CHx (x = 1, 2, 3) growth species for adsorption sites.