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Chen, Xiaochi,Huo, Yijie,Cho, Seongjae,Park, Byung-Gook,Harris, James S. Jr. The Institute of Electronics and Information Engin 2014 IEIE Transactions on Smart Processing & Computing Vol.3 No.5
Ge is becoming an increasingly popular semiconductor material with high Si compatibility for on-chip optical interconnect technology. For a better manifestation of the meritorious material properties of Ge, its surface treatment should be performed satisfactorily before the electronic and photonic components are fabricated. Ex-situ rapid thermal annealing (RTA) processes with different gases were carried out to examine the effects of the annealing gases on the thin-film quality of Ge grown epitaxially on Si substrates. The Ge-on-Si samples were prepared in different structures using the same equipment, reduced-pressure chemical vapor deposition (RPCVD), and the samples annealed in $N_2$, forming gas (FG), and $O_2$ were compared with the unannealed (deposited and only cleaned) samples to confirm the improvements in Ge quality. To evaluate the thin-film quality, room-temperature photoluminescence (PL) measurements were performed. Among the compared samples, the $O_2$-annealed samples showed the strongest PL signals, regardless of the sample structures, which shows that ex-situ RTA in the $O_2$ environment would be an effective technique for the surface treatment of Ge in fabricating Ge devices for optical computing systems.
Liu, Xiaochi,Qu, Deshun,Li, Hua-Min,Moon, Inyong,Ahmed, Faisal,Kim, Changsik,Lee, Myeongjin,Choi, Yongsuk,Cho, Jeong Ho,Hone, James C.,Yoo, Won Jong American Chemical Society 2017 ACS NANO Vol.11 No.9
<P>Diverse diode characteristics were observed in two (2D) black phosphorus (BP) and molybdenum disulfide (MoS2) heterojunctions. The characteristics of a backward rectifying diode, a Zener diode, and a forward rectifying diode were obtained from the heterojunction through-thickness modulation of the BP flake or back gate modulation. Moreover, a tunnel diode with a precursor to negative differential resistance can be realized by applying dual gating with a sad polymer electrolyte layer as a top gate dielectric material. Interestingly, a steep subthreshold swing Of 55 mV/dec was achieved in a top-gated 2D BP-MoS2 junction. Our simple device architecture and chemical doping-free processing guaranteed the device quality. This work helps us understand the fundamentals of tunneling in 2D semiconductor heterostructures and shows great potential in future applications in integrated low-power circuits.</P>
Choi, Min Sup,Qu, Deshun,Lee, Daeyeong,Liu, Xiaochi,Watanabe, Kenji,Taniguchi, Takashi,Yoo, Won Jong American Chemical Society 2014 ACS NANO Vol.8 No.9
<P>This paper demonstrates a technique to form a lateral homogeneous 2D MoS<SUB>2</SUB> p–n junction by partially stacking 2D h-BN as a mask to p-dope MoS<SUB>2</SUB>. The fabricated lateral MoS<SUB>2</SUB> p–n junction with asymmetric electrodes of Pd and Cr/Au displayed a highly efficient photoresponse (maximum external quantum efficiency of ∼7000%, specific detectivity of ∼5 × 10<SUP>10</SUP> Jones, and light switching ratio of ∼10<SUP>3</SUP>) and ideal rectifying behavior. The enhanced photoresponse and generation of open-circuit voltage (<I>V</I><SUB>OC</SUB>) and short-circuit current (<I>I</I><SUB>SC</SUB>) were understood to originate from the formation of a p–n junction after chemical doping. Due to the high photoresponse at low <I>V</I><SUB>D</SUB> and <I>V</I><SUB>G</SUB> attributed to its built-in potential, our MoS<SUB>2</SUB> p–n diode made progress toward the realization of low-power operating photodevices. Thus, this study suggests an effective way to form a lateral p–n junction by the h-BN hard masking technique and to improve the photoresponse of MoS<SUB>2</SUB> by the chemical doping process.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-9/nn503284n/production/images/medium/nn-2014-03284n_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn503284n'>ACS Electronic Supporting Info</A></P>
Monolayer Molybdenum Disulfide Transistors with Single-Atom-Thick Gates
Zhu, Yibo,Li, Yijun,Arefe, Ghidewon,Burke, Robert A.,Tan, Cheng,Hao, Yufeng,Liu, Xiaochi,Liu, Xue,Yoo, Won Jong,Dubey, Madan,Lin, Qiao,Hone, James C. American Chemical Society 2018 NANO LETTERS Vol.18 No.6
<P>Two-dimensional transition-metal dichalcogenides (TMDs) are unique candidates for the development of next-generation electronic devices. However, the large contact resistance between metal and the monolayer TMDs have significantly limited the devices’ performance. Also, the integration of ultrathin high-<I>k</I> dielectric layers with TMDs remains difficult due to the lack of dangling bonds on the surface of TMDs. We present monolayer molybdenum disulfide field-effect transistors with bottom local gates consisting of monolayer graphene. The atomic-level thickness and surface roughness of graphene facilitate the growth of high-quality ultrathin HfO<SUB>2</SUB> and suppress gate leakage. Strong displacement fields above 8 V/nm can be applied using a single graphene gate to electrostatically dope the MoS<SUB>2</SUB>, which reduces the contact resistances between Ni and monolayer MoS<SUB>2</SUB> to 2.3 kΩ·μm at low gate voltages. The devices exhibit excellent switching characteristics including a near-ideal subthreshold slope of 64 millivolts per decade, low threshold voltage (∼0.5 V), high channel conductance (>100 μS/μm), and low hysteresis. Scaled devices with 50 and 14 nm channels as well as ultrathin (5 nm) gate dielectrics show effective immunity to short-channel effects. The device fabricated on flexible polymeric substrate also exhibits high performance and has a fully transparent channel region that is desirable in optical-related studies and practical applications.</P> [FIG OMISSION]</BR>
Renjie Tu,Wenbiao Jin,Song-fang Han,Binbin Ding,Shu-hong Gao,Xu Zhou,Shao-feng Li,Xiaochi Feng,Qing Wang,Qinhui Yang,Yu Yuwen 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.5
Linear alkylbenzene sulfonate (LAS), which is widely used as detergent, is a common toxic pollutant in wastewater. Generally, biodegradation process is applied to remove LAS. However, the efficiency of traditional wastewater treatment cannot meet the growing demand. In this study, an improved biological turntable with a symbiotic system of bacteria and microalgae was primarily used to enhance the biodegradation efficiency of LAS from wastewater. The symbiotic system of bacteria and microalgae was mainly composed of Scenedesmus dimorphus and three LAS-degrading bacteria Plesiomonas sp. (L3, L7) and Pseudomonas sp. (H6). The average removal rate of LAS was up to 94.6%. The LAS concentration of the effluent of the system decreased by 81.7% after the bacterial-microalgae inoculation (the inoculation temperature was 25 oC; microalgae were inoculated at a concentration of 10% only at the start of the system; bacteria were continuously inoculated at 1‰ concentration). After bacterial-microalgae inoculation, the average effluent concentration of CODCr in the tertiary reaction tank was 24.3mg/L, the average membrane effluent concentration was 15.8mg/L, and the average removal rate was 90.5%. Compared with the control group without inoculation, the concentration of CODCr in the tertiary reaction tank and membrane effluent decreased by 55.7% and 46.4%. The denaturing gradient electrophoresis (DGGE) pattern analysis of the systemic flora showed that there were two dominant species of high LAS degrading bacteria. They were identified to belong to Plesiomonas sp. and Pseudomonas sp., respectively.
Xu Zhou,Wenbiao Jin,Lan Wang,Wanqing Ding,Chuan Chen,Xijun Xu,Renjie Tu,Song-fang Han,Xiaochi Feng,Duu-Jong Lee 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.9
Enhancement of sludge dewaterability is key for sludge management and disposal of wastewater treatment plants (WWTP). In this study, the Fe2+-peroxymonosulfate (PMS) conditioning approach was first used to oxidize the primary sludge from the primary sedimentation tank of a full scale WWTP. The combination of Fe2+ (0.05-0.5 g/g TSS) and PMS (0.05-0.5 g/g TSS) could significantly improve the dewaterability of primary sludge. The optimal addition amount of Fe2+ and PMS was 0.1 g/g TSS and 0.25 g/g TSS, respectively, under which the capillary suction time (CST) and specific resistance to filtration (SRF) of the sludge was reduced by 79% and 95%. The physicochemical properties (particle size, zeta potential, EPS composition) of the primary sludge before and after oxidative conditioning were measured. Results showed that sulfate radicals generated from Fe2+-PMS system effectively reduced organic matter in different EPS fractions, further destroying sludge floc cells. Then the bound water in the sludge flocs was released, thereby improving the sludge dewaterability. The microscopic morphology also indicated that the sludge flocs have a blocky structure with tight texture before conditioning. After conditioning, the sludge flocs become smaller, and many irregular pores are formed on the surface, which facilitates the passage of internal moisture. Economic analysis showed that Fe2++PMS conditioning is more economical than the traditional Fenton method.