衬底位置对制备二维的MoS2的影响

新型的二维层状材料凭借着其优异的机械、光学、电学等独特性能受到研究者广泛关注,二维层状材料如石墨烯、过渡金属硫族化合物等在柔性器件等领域具有潜在的应用前景,成为了现阶段研究热点之一;然而,应用的前提是高质量的二维材料大面积可控制备。利用化学气相沉积方法制备了二维的MoS_2,探讨了放置衬底的差异对合成二维的MoS_2的影响。结果表明,在其它相同的实验条件下,face-up和face-down的放置位置制备的MoS_2具有不同的形状、在衬底上的覆盖率不同;尽管如此,两种放置情况下,获得的单层的MoS_2具有类似的结构和荧光特性。研究结果对可控合成二维的MoS_2以及其它的TMDs均具有指导意义和参考价值。

Wet friction performance of C/C-SiC composites prepared by new processing route

C/C-SiC composites with SiC island distribution Were prepared via a new processing route. The fabrication process mainly included silicon infiltration by ultrasonic vibration, chemical vapor deposition （CVD）, siliconizing, liquid phase impregnation and carbonization. The wear and friction properties were tested by an MM-1000 wet friction machine. The results show that SiC phases are mainly distributed between carbon fibers and pyrocarbons as well as among the pryoearbons. The dynamic friction coefficient of the composites decreases gradually from 0.126 to 0.088 with the increase of the surface pressure from 0.5 to 2.5 MPa at the same rotary speed. Furthermore, under the constant surface pressure, the dynamic friction coefficient increases from 0.114 to 0.126 with the increase of the rotary speed from 1 500 to 2 500 r/min. However, the coefficient decreases to 0.104 when the rotary speed exceeds 4 500 r/min. During the friction process, the friction coefficient of C/C-SiC composite is between 0.088 and 0.126, and the wear value is zero after 300 times brake testing.

Preparation of N-Doped TiO_2-Loaded Halloysite Nanotubes and Its Photocatalytic Activity under Solar-Light Irradiation

The N-doped TiO2-loaded halloysite nanotubes(N-Ti O2/HNTs) nanocomposites were prepared by using chemical vapor deposition method which was realized in autoclave. The photocatalytic activity of nanocomposites was evaluated by virtue of the decomposition of formaldehyde gas under solar-light irradiation. The XRD patterns verified that the anatase structured TiO2 was deposited on HNTs. The TEM images showed that the surface of HNTs was covered with nanosized TiO2 with a particle size of ca. 20 nm. The UV-vis spectra indicated that the N-Ti O2/HNTs presented a significant absorption band in the visible region between 400 nm and 600 nm. Under solar-light irradiation, the highest degradation rate of formaldehyde gas attained 90% after 100 min of solar-light irradiation. The combination of the photocatalytic property of TiO2 and the unique structure of halloysite would assert a promising perspective in degradation of organic pollutants.

Preparation and characterization of In_(0.82)Ga_(0.18)As PIN photodetectors

Using two-step growth method and buffer layer annealing treatment,the double heterojunction structures of In_(0.82)Ga_(0.18) As epilayer capped with In As_(0.6)P0.4 layer were prepared on In P substrate by low pressure metal organic chemical vapor deposition(LP-MOCVD).Based on the high quality In_(0.82)Ga_(0.18) As structures,the In_(0.82)Ga_(0.18) As PIN photodetector with cut-off wavelength of 2.56 μm at room temperature was fabricated by planar semiconductor technology,and the device performance was investigated in detail.The typical dark current at the reverse bias VR=10 m V and the resistance area product R0 A are 5.02 μA and 0.29 ?·cm2 at 296 K and 5.98 n A and 405.2 ?·cm2 at 116 K,respectively.The calculated peak detectivities of the In_(0.82)Ga_(0.18) As photodetector are 1.21×1010 cm·Hz1/2/W at 296 K and 4.39×1011 cm·Hz1/2/W at 116 K respectively,where the quantum efficiency η=0.7 at peak wavelength is supposed.The results show that the detection performance of In_(0.82)Ga_(0.18) As prepared by two-step growth method can be improved greatly.