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CdTe thin film grown by MOCVD
Abstracts
and X R D measurements show that there are serious interdiffusion and interface reactions in samples annealed at temperatures higher than 650°C. The possible reaction products are Ba2SiO4 and Ba3SiOs. No new chemical compound related to copper was found. RBS measurements show that Cu ions diffused deeply into Si(100) substrate and play the role of a fast diffuser and Ba ions are concentrated in an area near the interface. The result of AES measurement is in agreement with that of RBS measurements. A thin layer of ZrO2 may slow down the interdiffusion process significantly.
structure. The infrared spectrum of AISt3 monolayers in the multilayer has been measured by Fourier transform infrared spectroscopy monolayers. The absorption intensity of CH2 stretching vibration vs AISt3 layer number is compared with optical multilayer calculation. The periodic structure of the hybrid multilayer is revealed by low angle X-ray diffraction. These show that the arrangement of A1St3 film deposited on a new solid surface of A1203 film is the same as that on the initial substrate surface. It is suggested that this method for building a L-B film/alumina multilayer structure could be applied to the study of nonlinear optical properties of Langmuir-Blodgett films.
The tantalum/aluminum alloy resistive film containing aluminum 50 at% Study of behaviour of metal clusters on substrates with STM Yang Bangchao and Jia Yuming, University of Electronic Science
and Technology of Chengdu, Chengdu 610054, China In this paper, both the tantalum/aluminum alloy resistive film containing aluminum 50 at% and the mid-power thin-film attenuator used for microwave circuits are studied and analyzed. The Ta/A1 alloy film containing A1 50 at% has high resistance stability. The alloy film is deposited by sputtering from a tantalum cathode which is covered partly by aluminum discs. The aluminum part of the target area is approximately 43% of the total. It is found that the alloy film could be used for a stable power resistor and its network. The main properties of the resistor as follows : atomic content Ta:A1 = 53.7:46.3; specific resistivity, 150-300 # ~ cm; temperature coefficient of resistance - 7 0 + 2 0 ppm '~C- ~; aged at 200°C for 96 h R/R < 0.3% ; and temperature circle ( - 1 0 to +200°C/5 times) R/R < 0.5%. The mid-power thin film attenuator used for microwave circuits is also described in this paper. This attenuator is made from the Ta/A1 alloy film containing aluminum 50 at%. The formula derived for attenuation and characteristic impedance of attenuator with n-tape network pattern will prove to be of benefit for the design of thin-film attenuators. The design of power or midpower thin-film attenuator has been discussed. Finally, the fabrication and assembly of the attenuator have been introduced. The indexes of the annenuator are : dimension 13.86 x 13.40 x 0.60 mm; power loading 25 W ; average power density 1.75 W mm 2; maximum power density 3.8 W m m - 2 ; attenuation 11.5 dB; characteristic impedance 50; frequency range 0-540 MHz ; and voltage standing-wave ratio < 1.08. The results above indicate that the mid-power thin-film attenuator has satisfied the demands of the user completely and it has not been previously reported in our country.
Study of CH2 stretching vibration in AISt3 L-B film/alumina hybrid multilayer by infrared spectroscopy
Wang Dongsheng, Ma Zili, Xue Zengquan and Wu Quande,
Department of Radio-Electronics, Peking University and Beo'ing Laboralory of Vacuum Physics, Academia Sinica, Beo'ing 100871, China Clusters are small particles whose size is less than l 0 3 /~. They possess special characteristics compared with the same bulk element material. Sometimes we find some clusters on the deposited thin films. These clusters will affect the structures and characteristics of the films, especially in semiconductor devices, where they will affect device quality. A scanning tunnelling microscope (STM) possesses atom level resolution for analysing sample surfaces. It is an important tool for studying the cluster behaviour on the substrates. We have deposited gold (Au) on the substrates of mica and silicon (Si) in a high vacuum chamber. The thickness of thin films is about 50-500 A. The samples are taken out from the chamber and put into the sample holder of the STM. We analysed these samples in air at room temperature. We have observed gold cluster structures and motion behaviour on the (001) plane of mica which cleaved in air. The thickness of gold thin film is about 400 A. On this thin film, there are clusters and these clusters move randomly with time. Similarly we observed gold clusters on one (111) plane of the Si wafer. Before depositing the gold thin film, we cleaned the Si wafer with a chemical clean technique. The thickness of gold thin films is about 50-400 A. On the (111) plane of the Si wafer, gold clusters also move randomly with time. We analysed these samples with Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). After that, we discuss these results and the random motion mechanism of these clusters.
Investigation of the interface of a HgCdTe/CdTe thin film grown by MOCVD
Zheng Tianshui, Liu Liying, Xing Zhongjing, Wang Wencheng, Shen Yuanlma and Zhang Zhiming, Laboratory of Laser Physics
K J Ma, Z Z Yu, J Q Yong and S Z Shen, Shanghai Institute of
and Optics, Department of Physics, Fudan University, Shanghai 200433, China
and Song Xiang-yun, Shanghai Institute of Ceramics, Academia
Technical Physics, Academia Sinica, Shanghai 200083, China; Sinica, Shanghai 200050, China
Four to six monolayers of AISt3 Langmuir-Blodgett (L-B) film and one layer of thermal deposited 3.5-6 nm-thick A1203 film alternatively form a hybrid A1St3/A1203 modulated multilayer
The interface of a HgCdTe/CdTe thin film grown by MOCVD was investigated by high resolution electron microscopy. It is 1073
Abstracts
shown that there is no sharp boundary between HgCdTe and CdTe films. It is filled with small order and disorder areas in the interface region with a width of 1000-1500 A. Two sets of electronic diffraction patterns have been observed. The disorder areas can be changed into an order one under long time electron beam radiation.
AR layer properties for high-power laser prepared by neutralsolution processing Wu Fanfeng and Su Kailong, Shanghai Institute of Optics and
Fine Mechanics, Academia Sinica, Shanghai 201800, China The AR layer on BK-7 glass substrate has been prepared by neutral-solution processing. Polished BK-7 substrate 30 mm in diameter and 4 mm thick was prepared and cleaned before treatment. The substrate was immersed in a neutral solution of 0.05 M Na2HPO4 in distilled water at 60 or 80°C in a constant temperature bath. The wavelength of minimum reflectance increased linearly with increasing processing time on the condition that the concentration and temperature of the solution are constant. After withdrawing the substrate from the neutral-solution, the substrate was transferred to distilled water for several minutes followed by soaking in anhydrous alcohol and vacuum drying. Some properties of the AR layer have been measured. (1) Transmittance and reflectance. A broad region of high transmittance had been obtained due to the gradual refractive index on substrate. The maximum transmittance of 99.5% and minimum reflectance of 0.15%/surface at 1.06/~m were obtained. It shows the optical loss is low. (2) Laser damage threshold. Measurement of the laser damage threshold with 10 ns pulses 90 #m beam spot at 1.06/~m from a N d : Y A G laser damage threshold of 17.5 J cm -2 has been obtained, it is nearly twice the highest laser damage threshold of 10 J cm-2 for the AR film prepared by the vacuum evaporation method. (3) Structures of the AR layer. The growing structures of the AR layer on substrate have been observed by TEM. It seemed different with the columned structure in films by vacuum evaporation and likes a networking structure and the surface roughness is small.
Optical study on interface property of MBE Hgl_xCdxTe/CdTe/ GaAs layers Liu Weijun, Zhu Jinbin, Shi Guoliang and Liu Pulin, National
Laboratory for Infrared Physics, Academia Sinica, Shanghai 200083, China ; and He Li, Xie Qinxi and Yuan Shixin, Shanghai Institute of Technical Physics, Academia S&ica, Shanghai 200083, China Hg~ xCdxTe/CdTe/GaAs layers grown by the MBE technique are a very promising material for detection of infrared photon, compared with bulk Hg~_xCd~Te crystal. However, there are quite a lot of problems unsolved in material growth techniques and physics. Having a large lattice mismatch between Hg ~ xCdxTe and GaAs substrate, it is very difficult to obtain high quality Hg~ ~CdxTe/GaAs layers. Though transmission electron 1074
microscopy and an electron probe are usually used to check the distribution of composition and interface integrity, the information obtained from them is not sufficient to explain the material performances. As we know, in mixed crystal the disorder can activate the low frequency phonon, therefore the far infrared reflection spectra can be used to study the low frequency lattice vibration behavior. In this paper, we propose that the far infrared reflection spectrum can be used to study the disorder effect enhanced by the interface in Hga_xCdxTe/GaAs layers. The information of interface quality and its physics can be obtained from the phonon behavior which is very sensitive to the force constant within about 50 A. We report here the reflection spectra of a series of samples in the energy range from 20 to 370 cm ~ and at the temperature ranging from 4.2 to 300 K. Some reflection peaks were observed in the range from 20 to 110 cm i, and there is no frequency shift for these peaks with temperature, but obvious differences with various samples were observed. We assign these peaks to the lattice vibration behavior activated by the interface enhanced disorder. Our experimental results show that the interfaces of Hg 1- xCdxTe/CdTe/GaAs layers could be studied by means of reflection spectra. In addition, we measured the transport phenomena of these samples, and the influence of interface enhanced disorder on electrical parameters was discussed.
Interface properties of a-C: H/a-SiOx: H multilayers Cui Jingbiao and Zhang Weiping, Department of Physics, Uni-
versity Science and Technology of China, Hefei 230026, China Amorphous multilayer thin films of a-C:H/a-SiOx:H were deposited by rf magnetron sputtering. The interface properties were analyzed by X-ray diffraction, Auger depth profile and infrared absorption measurements. X-ray diffraction and Auger depth profile results demonstrate that smooth parallel and uniform layers with sharper interface are achievable. The interfacial roughness was estimated from X-ray diffraction according to the theory that the X-ray diffraction intensity G,, (~) of real multilayers is reduced by a factor P,,(~) from the ideal case Im because of the interface incoherent scattering, where ~ is interfacial roughness parameter and m is the order of diffraction peak. Gm(~) can be obtained theoretically by this consideration. By comparing the intensities given in theory with the experimental values it is possible to determine 4. The calculated value of ~ for one sample is 5.8 A. The Auger depth profile shows very good periodicity. The silicon and oxygen peaks oscillate 180° out of phase with carbon peaks. The interfacial roughness can be estimated from the Auger depth profile. The changing region of the curves from maximum to minimum is regarded as interface etching time, and the ratio between interface etching time t~ and one period etching time tp can be obtained. Using the modulation period d, the interfacial roughness estimated by this method is 7.8 A (sample used for Auger depth profile is not that for X-ray diffraction). The bonding configuration of C and Si atoms at the interface was observed in infrared absorption measurements. There is one absorption peak at 780 cm- ~ corresponding to the Si--C bond formed at the interface.
and X R D measurements show that there are serious interdiffusion and interface reactions in samples annealed at temperatures higher than 650°C. The possible reaction products are Ba2SiO4 and Ba3SiOs. No new chemical compound related to copper was found. RBS measurements show that Cu ions diffused deeply into Si(100) substrate and play the role of a fast diffuser and Ba ions are concentrated in an area near the interface. The result of AES measurement is in agreement with that of RBS measurements. A thin layer of ZrO2 may slow down the interdiffusion process significantly.
structure. The infrared spectrum of AISt3 monolayers in the multilayer has been measured by Fourier transform infrared spectroscopy monolayers. The absorption intensity of CH2 stretching vibration vs AISt3 layer number is compared with optical multilayer calculation. The periodic structure of the hybrid multilayer is revealed by low angle X-ray diffraction. These show that the arrangement of A1St3 film deposited on a new solid surface of A1203 film is the same as that on the initial substrate surface. It is suggested that this method for building a L-B film/alumina multilayer structure could be applied to the study of nonlinear optical properties of Langmuir-Blodgett films.
The tantalum/aluminum alloy resistive film containing aluminum 50 at% Study of behaviour of metal clusters on substrates with STM Yang Bangchao and Jia Yuming, University of Electronic Science
and Technology of Chengdu, Chengdu 610054, China In this paper, both the tantalum/aluminum alloy resistive film containing aluminum 50 at% and the mid-power thin-film attenuator used for microwave circuits are studied and analyzed. The Ta/A1 alloy film containing A1 50 at% has high resistance stability. The alloy film is deposited by sputtering from a tantalum cathode which is covered partly by aluminum discs. The aluminum part of the target area is approximately 43% of the total. It is found that the alloy film could be used for a stable power resistor and its network. The main properties of the resistor as follows : atomic content Ta:A1 = 53.7:46.3; specific resistivity, 150-300 # ~ cm; temperature coefficient of resistance - 7 0 + 2 0 ppm '~C- ~; aged at 200°C for 96 h R/R < 0.3% ; and temperature circle ( - 1 0 to +200°C/5 times) R/R < 0.5%. The mid-power thin film attenuator used for microwave circuits is also described in this paper. This attenuator is made from the Ta/A1 alloy film containing aluminum 50 at%. The formula derived for attenuation and characteristic impedance of attenuator with n-tape network pattern will prove to be of benefit for the design of thin-film attenuators. The design of power or midpower thin-film attenuator has been discussed. Finally, the fabrication and assembly of the attenuator have been introduced. The indexes of the annenuator are : dimension 13.86 x 13.40 x 0.60 mm; power loading 25 W ; average power density 1.75 W mm 2; maximum power density 3.8 W m m - 2 ; attenuation 11.5 dB; characteristic impedance 50; frequency range 0-540 MHz ; and voltage standing-wave ratio < 1.08. The results above indicate that the mid-power thin-film attenuator has satisfied the demands of the user completely and it has not been previously reported in our country.
Study of CH2 stretching vibration in AISt3 L-B film/alumina hybrid multilayer by infrared spectroscopy
Wang Dongsheng, Ma Zili, Xue Zengquan and Wu Quande,
Department of Radio-Electronics, Peking University and Beo'ing Laboralory of Vacuum Physics, Academia Sinica, Beo'ing 100871, China Clusters are small particles whose size is less than l 0 3 /~. They possess special characteristics compared with the same bulk element material. Sometimes we find some clusters on the deposited thin films. These clusters will affect the structures and characteristics of the films, especially in semiconductor devices, where they will affect device quality. A scanning tunnelling microscope (STM) possesses atom level resolution for analysing sample surfaces. It is an important tool for studying the cluster behaviour on the substrates. We have deposited gold (Au) on the substrates of mica and silicon (Si) in a high vacuum chamber. The thickness of thin films is about 50-500 A. The samples are taken out from the chamber and put into the sample holder of the STM. We analysed these samples in air at room temperature. We have observed gold cluster structures and motion behaviour on the (001) plane of mica which cleaved in air. The thickness of gold thin film is about 400 A. On this thin film, there are clusters and these clusters move randomly with time. Similarly we observed gold clusters on one (111) plane of the Si wafer. Before depositing the gold thin film, we cleaned the Si wafer with a chemical clean technique. The thickness of gold thin films is about 50-400 A. On the (111) plane of the Si wafer, gold clusters also move randomly with time. We analysed these samples with Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). After that, we discuss these results and the random motion mechanism of these clusters.
Investigation of the interface of a HgCdTe/CdTe thin film grown by MOCVD
Zheng Tianshui, Liu Liying, Xing Zhongjing, Wang Wencheng, Shen Yuanlma and Zhang Zhiming, Laboratory of Laser Physics
K J Ma, Z Z Yu, J Q Yong and S Z Shen, Shanghai Institute of
and Optics, Department of Physics, Fudan University, Shanghai 200433, China
and Song Xiang-yun, Shanghai Institute of Ceramics, Academia
Technical Physics, Academia Sinica, Shanghai 200083, China; Sinica, Shanghai 200050, China
Four to six monolayers of AISt3 Langmuir-Blodgett (L-B) film and one layer of thermal deposited 3.5-6 nm-thick A1203 film alternatively form a hybrid A1St3/A1203 modulated multilayer
The interface of a HgCdTe/CdTe thin film grown by MOCVD was investigated by high resolution electron microscopy. It is 1073
Abstracts
shown that there is no sharp boundary between HgCdTe and CdTe films. It is filled with small order and disorder areas in the interface region with a width of 1000-1500 A. Two sets of electronic diffraction patterns have been observed. The disorder areas can be changed into an order one under long time electron beam radiation.
AR layer properties for high-power laser prepared by neutralsolution processing Wu Fanfeng and Su Kailong, Shanghai Institute of Optics and
Fine Mechanics, Academia Sinica, Shanghai 201800, China The AR layer on BK-7 glass substrate has been prepared by neutral-solution processing. Polished BK-7 substrate 30 mm in diameter and 4 mm thick was prepared and cleaned before treatment. The substrate was immersed in a neutral solution of 0.05 M Na2HPO4 in distilled water at 60 or 80°C in a constant temperature bath. The wavelength of minimum reflectance increased linearly with increasing processing time on the condition that the concentration and temperature of the solution are constant. After withdrawing the substrate from the neutral-solution, the substrate was transferred to distilled water for several minutes followed by soaking in anhydrous alcohol and vacuum drying. Some properties of the AR layer have been measured. (1) Transmittance and reflectance. A broad region of high transmittance had been obtained due to the gradual refractive index on substrate. The maximum transmittance of 99.5% and minimum reflectance of 0.15%/surface at 1.06/~m were obtained. It shows the optical loss is low. (2) Laser damage threshold. Measurement of the laser damage threshold with 10 ns pulses 90 #m beam spot at 1.06/~m from a N d : Y A G laser damage threshold of 17.5 J cm -2 has been obtained, it is nearly twice the highest laser damage threshold of 10 J cm-2 for the AR film prepared by the vacuum evaporation method. (3) Structures of the AR layer. The growing structures of the AR layer on substrate have been observed by TEM. It seemed different with the columned structure in films by vacuum evaporation and likes a networking structure and the surface roughness is small.
Optical study on interface property of MBE Hgl_xCdxTe/CdTe/ GaAs layers Liu Weijun, Zhu Jinbin, Shi Guoliang and Liu Pulin, National
Laboratory for Infrared Physics, Academia Sinica, Shanghai 200083, China ; and He Li, Xie Qinxi and Yuan Shixin, Shanghai Institute of Technical Physics, Academia S&ica, Shanghai 200083, China Hg~ xCdxTe/CdTe/GaAs layers grown by the MBE technique are a very promising material for detection of infrared photon, compared with bulk Hg~_xCd~Te crystal. However, there are quite a lot of problems unsolved in material growth techniques and physics. Having a large lattice mismatch between Hg ~ xCdxTe and GaAs substrate, it is very difficult to obtain high quality Hg~ ~CdxTe/GaAs layers. Though transmission electron 1074
microscopy and an electron probe are usually used to check the distribution of composition and interface integrity, the information obtained from them is not sufficient to explain the material performances. As we know, in mixed crystal the disorder can activate the low frequency phonon, therefore the far infrared reflection spectra can be used to study the low frequency lattice vibration behavior. In this paper, we propose that the far infrared reflection spectrum can be used to study the disorder effect enhanced by the interface in Hga_xCdxTe/GaAs layers. The information of interface quality and its physics can be obtained from the phonon behavior which is very sensitive to the force constant within about 50 A. We report here the reflection spectra of a series of samples in the energy range from 20 to 370 cm ~ and at the temperature ranging from 4.2 to 300 K. Some reflection peaks were observed in the range from 20 to 110 cm i, and there is no frequency shift for these peaks with temperature, but obvious differences with various samples were observed. We assign these peaks to the lattice vibration behavior activated by the interface enhanced disorder. Our experimental results show that the interfaces of Hg 1- xCdxTe/CdTe/GaAs layers could be studied by means of reflection spectra. In addition, we measured the transport phenomena of these samples, and the influence of interface enhanced disorder on electrical parameters was discussed.
Interface properties of a-C: H/a-SiOx: H multilayers Cui Jingbiao and Zhang Weiping, Department of Physics, Uni-
versity Science and Technology of China, Hefei 230026, China Amorphous multilayer thin films of a-C:H/a-SiOx:H were deposited by rf magnetron sputtering. The interface properties were analyzed by X-ray diffraction, Auger depth profile and infrared absorption measurements. X-ray diffraction and Auger depth profile results demonstrate that smooth parallel and uniform layers with sharper interface are achievable. The interfacial roughness was estimated from X-ray diffraction according to the theory that the X-ray diffraction intensity G,, (~) of real multilayers is reduced by a factor P,,(~) from the ideal case Im because of the interface incoherent scattering, where ~ is interfacial roughness parameter and m is the order of diffraction peak. Gm(~) can be obtained theoretically by this consideration. By comparing the intensities given in theory with the experimental values it is possible to determine 4. The calculated value of ~ for one sample is 5.8 A. The Auger depth profile shows very good periodicity. The silicon and oxygen peaks oscillate 180° out of phase with carbon peaks. The interfacial roughness can be estimated from the Auger depth profile. The changing region of the curves from maximum to minimum is regarded as interface etching time, and the ratio between interface etching time t~ and one period etching time tp can be obtained. Using the modulation period d, the interfacial roughness estimated by this method is 7.8 A (sample used for Auger depth profile is not that for X-ray diffraction). The bonding configuration of C and Si atoms at the interface was observed in infrared absorption measurements. There is one absorption peak at 780 cm- ~ corresponding to the Si--C bond formed at the interface.