Alkali metal has predicted to be a promising candidate for decorating silicene surface to obtain the high hydrogen storage capacity, owing to their physical properties of lightweight, lower cohesive energy, and appropriate strength of the interaction with H₂ molecules. However, though the high potential in hydrogen storage of alkali metal adatoms-decorated silicene under the fixed adatom adsorption component is well known, the evidence for the hydrogen storage capacity of alkali metal adatoms-decorated silicene under different adatom adsorption components remains largely unexplored, which may be of great significance to make the most advantages of alkali metal adatoms-decorated silicene in hydrogen storage aspects. Herein, according to the first-principles calculation corrected by the van der Waals effect, we take Lidecorated silicene for example and perform the detailed study of the geometry structure, the stability and the hydrogen storage capacity of silicene under different Li adsorption components (Li_xSi_1-x), aiming to maximize the hydrogen storage performance of Li-decorated silicene. The results show that the preferred site of Li changes from the hollow site to the valley site as the Li component increases from 0.11 to 0.50, and binding energy of Li is always greater than the corresponding cohesive energy, showing the high stability of Li-decorated silicene and the feasibility of the method to obtain a higher hydrogen storage capacity by increasing the Li component. The hydrogen storage of silicene under different Li adsorption components is investigated by the sequential addition of H₂ molecules nearby Li atoms in a stepwise manner. It can be observed that the hydrogen storage capacity of Li-decorated silicene increases and the average adsorption energy decreases with the increase of the Li component. The corresponding hydrogen storage capacities of Li_0.11Si_0.89, Li_0.20Si_0.80, Li_0.33Si_0.67, Li_0.43Si_0.57 can reach up to 2.54 wt%, 4.82 wt%, 6.00 wt% and 9.58 wt% with 0.58 eV/H₂, 0.47 eV/H₂, 0.54 eV/H₂ and 0.41 eV/H₂ average adsorption energy, respectively. When the Li component increases up to 0.50, Li atoms are saturated with a maximum hydrogen storage capacity of 11.46 wt% and an average adsorption energy of 0.34 eV/H₂, which well meet the hydrogen storage standard set by the U.S. Department of Energy and mean that the hydrogen storage can be theoretically improved by increasing the Li adsorption component to a saturated level. Furthermore, we analyze the Mulliken charge population, the charge density difference and the density of states, showing that the charge-induced electrostatic interaction and the orbital hybridization are the key factors for the hydrogen adsorption of Li-decorated silicene. Our results may enhance our fundamental understanding of the hydrogen storage mechanism and explore the applications in areas of hydrogen storage for Li-decorated silicene, which are of great importance for the usage of hydrogen in the future.

Zhe Sheng;显英 戴;Dong Ming Miao;Shu Jing Wu;Tian Long Zhao;跃 郝

Wuli Xuebao/Acta Physica Sinica

2018-5-20

In this paper, the influence of Cl-based gate recess depth on the control of the threshold voltage of AlGaN/GaN Fin-HEMTs by varying the fin width is investigated. When combining Cl-based gate recess technology and the modulation of fin width, as gate recess depth increases, the influence of fin width on the threshold voltage of Fin-HEMTs is diminished. It is implied that the influence of Cl-based gate recess and fin width on the threshold voltage is coupled. It is also instructive and meaningful for the threshold voltage control of AlGaN/GaN Fin-HEMTs by combining Cl-based gate recess and the modulation of fin width.

Meng Zhang;Bing Hou;Qing Zhu;Lixiang Chen;Ling Yang;Jiejie Zhu;Xiaohua Ma;Minhan Mi;Mei Wu;跃 郝

2018-5

We propose a photonic spiking neural network (SNN) consisting of photonic spiking neurons based on vertical-cavity surface-emitting lasers (VCSELs). The photonic spike timing dependent plasticity (STDP) is implemented in a vertical-cavity semiconductor optical amplifier (VCSOA). A versatile computational model of the photonic SNN is presented based on the rate equation models. Through numerical simulation, a spike pattern learning and recognition task is performed based on the photonic STDP. The results show that the post-synaptic spike timing (PST) is eventually converged iteratively to the first spike timing of the input spike pattern via unsupervised learning. Additionally, the convergence rate of the PST can be accelerated for a photonic SNN with more pre-synaptic neurons. The effects of VCSOA parameters on the convergence performance of the unsupervised spike learning are also considered. To the best of our knowledge, such a versatile computational model of photonic SNN for unsupervised learning and recognition of arbitrary spike pattern has not yet been reported, which would contribute one step forward toward numerical implementation of a large-scale energy-efficient photonic SNN, and hence is interesting for neuromorphic photonic systems and spiking information processing.

Shuiying Xiang;Yahui Zhang;Junkai Gong;Xingxing Guo;Lin Lin;跃 郝

IEEE Journal of Selected Topics in Quantum Electronics

2019-11-1

In the preparation of PSCs, NiOx is considered to be one very promising hole transport layers for its intrinsic p-type doping nature, deep-lying valence band, and high light transmittance. However, the thickness, uniformity, and composition of the NiOx film are not easy to accurately control by the solution spin-coating process. In this work, instead of the solution-processed NiOx, metal Ni is first deposited on the FTO/glass substrate by an e-beam evaporator and then converted to the NiOx by exposing it in the air with the help of annealing, which avoids the usage of a toxic solvent in the solution method. The deposition thickness and composition of the NiOx films could be well controlled. The results demonstrate that the Ni-oxidized NiOx HTL shows wonderful energy alignment, better charge extraction capability, and great efficiency in photoluminescence quenching when in contact with the perovskite film. By combining the two-step solution process method, high-performance PSC has been achieved based on the Ni-oxidized NiOx HTL, which is well above that based on the PEDOT:PSS and the solution-processed NiOx. Also, transient photocurrent (TPC) and transient photovoltage (TPV) measurements demonstrate that the device based on the Ni-oxidized NiOx HTL possesses a suppressed charge recombination and an outstanding ability of charge extraction. Furthermore, the Ni-oxidized NiOx-based devices exhibit better stability compared to the devices based on solution-processed NiOx and PEDOT:PSS HTL. All the results show that the Ni oxidation method is an efficient method to prepare the NiOx HTL in PSCs.

Shangzheng Pang;Chunfu Zhang;Hang Dong;Dazheng Chen;Weidong Zhu;He Xi;Jingjing Chang;Zhenhua Lin;进成 张;跃 郝

ACS Applied Energy Materials

2019-7-22

Planar perovskite solar cells (PSCs) with perovskite and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) heterojunction have attracted much interest because they can be fabricated by a low-temperature process and exhibit high power conversion efficiency (PCE). Various compositional engineering and interface engineering approaches have been applied to produce high-performance PSC devices. In this study, we found that high-quality lead halide crystal precursor has a significant effect on the perovskite film quality and it could enhance perovskite film light absorption, reduce crystal defects, and suppress charge recombination, resulting in enhanced device performance (from 8.9 to 15.0% for CH₃NH₃PbI₃ and from 14.2 to 18.0% for MA_0.7FA_0.3PbI_3-xCl_x). Moreover, electron and hole interlayer free devices were achieved by using high-quality PbI₂ crystals and the devices exhibited a high PCE of 13.6 and 10.4% for glass and flexible substrates, respectively. This is important for simplifying the perovskite solar cell fabrication process without complex interface engineering involved, especially for printed PSCs.

Kaixuan Wang;Zhenhua Lin;Jing Ma;Ziye Liu;Long Zhou;Jianhui Du;Dazheng Chen;Chunfu Zhang;Jingjing Chang;跃 郝

ACS Omega

2017-9-30

Nonpolar a-plane [112̄0] GaN has been grown on r-plane [11̄02] sapphire by MOCVD, and investigated by high resolution X-ray diffraction and atomic force microscopy. As opposed to the c-direction, this particular orientation is non-polar, and it avoids polarization charge, the associated screening charge and the consequent band bending. Both low-temperature GaN buffer and high-temperature AlN buffer are used for a-plane GaN growth on r-plane sapphire, and the triangular pits and pleat morphology come forth with different buffers, the possible reasons for which are discussed. The triangular and pleat direction are also investigated. A novel modulate buffer is used for a-plane GaN growth on r-plane sapphire, and with this technique, the crystal quality has been greatly improved.

Shengrui Xu;跃 郝;Huantao Duan;进成 张;金风 张;Xiaowei Zhou;Zhiming Li;Jinyu Ni

Journal of Semiconductors

2009

The behaviors of the gate induced drain leakage (GIDL) stress during the single and alternating stresses were investigated. A combination of threshold voltage Vth and GIDL current Igidl has been applied to investigate n -channel metal-oxide-semiconductor field-effect transistors with different gate oxide thicknesses. The recovery and enhancement of Vth depending on the gate oxide thickness, are found to result from the GIDL stress in the two processes. This study reveals that different behaviors of GIDL stress for different gate oxide thicknesses are attributed to the rivalship between the hole-induced carrier mobility increase and the interface states-induced increase in lightly doped drain resistance.

X. H. Ma;艳荣 曹;海霞 高;H. F. Chen;跃 郝

Applied Physics Letters

2009

In this paper, we presented AlGaN/GaN MIS-HEMT with a 6-nm ALD La₂O₃ as gate insulator. The gate leakage current had been greatly reduced at both positive and negative bias by using La₂O₃ gate dielectric. Threshold voltage for MIS-HEMT moved +1 V toward positive direction compared with the Schottky gate HEMT (HEMT) demonstrating the negatively fixed charges at La₂O₃/AlGaN interface. Besides, the transconductance of MIS-HEMT was not degraded. The stability of fixed and trap state introduced by La₂O₃ gate dielectric was discussed.

Minhan Mi;Yunlong He;Bin Hou;Meng Zhang;进成 张;Chong Wang;Xiaohua Ma;跃 郝

Physica Status Solidi (C) Current Topics in Solid State Physics

2016-5-1

AlGaN/GaN high electron mobility transistors (HEMT) unpassivated with different gate lengths are irradiated with ⁶⁰Co γ-rays to doses up to 1 Mrad (Si). The bigger the doses are and the smaller the gate lengthis, the greater the changes in drain current and transconductanceare. While the gate leakage current is significantly increased after irradiation, the threshold voltage is relatively unaffected. By analysing the series resistance of channel and the threshold voltage, we find that irradiation induced electronegative surface state charges is one of the important reasons of radiation damage.

Wen Ping Gu;进成 张;Chong Wang;Qian Feng;Xiao Hua Ma;跃 郝

Wuli Xuebao/Acta Physica Sinica

2009-2

AlGaN/GaN depletion-mode high-electron-mobility transistor (D-HEMT) and fluorine (F) plasma treated enhancement-mode high-electron-mobility transistor (E-HEMT) are exposed to ⁶⁰Co gamma radiation with a dose of 1.6 Mrad (Si). No degradation is observed in the performance of D-HEMT. However, the maximum transconductance of E-HEMT is increased after radiation. The 2DEG density and the mobility are calculated from the results of capacitance-voltage measurement. The electron mobility decreases after fluorine plasma treatment and recovers after radiation. Conductance measurements in a frequency range from 10 kHz to 1 MHz are used to characterize the trapping effects in the devices. A new type of trap is observed in the F plasma treated E-HEMT compared with the D-HEMT, but the density of the trap decreases by radiation. Fitting of G _p/ω, data yields the trap densities D_T = (1 - 3) ×, 10¹² cm^-2 eV^-1 and D_T = (0.2 - 0.8) ×, 10¹² cm^-2 eV^-1 before and after radiation, respectively. The time constant is 0.5 ms-6 ms. With F plasma treatment, the trap is introduced by etch damage and degrades the electronic mobility. After ⁶⁰Co gamma radiation, the etch damage decreases and the electron mobility is improved. The gamma radiation can recover the etch damage caused by F plasma treatment.

Si Quan;跃 郝;Xiao Hua Ma;Hui You Yu

Chinese Physics B

2011-5