29,305 research outputs found
Fabrication and characterisation of novel Ge MOSFETs
No full textAs high-k dielectrics are introduced into commercial Si CMOS (Complimentary Metal Oxide Semiconductor) microelectronics, the 40 year channel/dielectric partnership of Si/SiO2 is ended and the door opened for silicon to be replaced as the active channel material in MOSFETs (Metal Oxide Semiconductor Field Effect Transistor). Germanium is a good candidate as it has higher bulk carrier mobilities than silicon. In addition, Si and Ge form a thermodynamically stable SiGe alloy of any composition, allowing Ge to be implemented as a thin layer on the surface of a standard Si substrate. This thesis is a practical investigation on several aspects of Ge CMOS technology.
High-k dielectric Ge p-MOSFETs are electrically characterised. A large variation in interface state densities is demonstrated to be responsible for a threshold voltage shift and this is proportional to reciprocal peak mobility due to the Coulomb scattering of carriers by charged states. A theoretical mobility is fitted to that measured at 4.2 K and confirms that interface states are the main source of interface charged impurities.
The model demonstrates a reduction in the interface charged impurity density in p-MOSFETs that underwent a PMA (Post Metallisation Anneal) in hydrogen atmosphere and that the anneal also reduces the RMS (Root Mean Square) dielectric/semiconductor interface roughness, from an average of 0.60 nm to 0.48 nm.
High-k strained Ge p-MOSFETs are electrically characterised and have peak mobilities at 300 K (470 cm2 V-1 s-1) and 4.2 K (1780 cm2 V-1 s-1) far in excess of those measured for the unstrained Ge p-MOSFETs (285 cm2 V-1 s-1,785 cm2 V-1 s-1 respectively). Strained Ge n-MOSFETs perform significantly worse than standard Si P, - MOSFETs primarily due to a high source/drain resistance.
A 10 nm thick SiGe-01 (On Insulator) layer with a Ge composition of 58% is obtained from a 55 nm Si0_88Ge1o2. initial layer on 100 nm Si-Ol substrate via the germanium condensation technique. For the first time, germanium is demonstrated to diffuse through the BOX (Buried OXide) during Ge-condensation and into the underlying Si substrate. An order of magnitude increase in the calculated ITOX (Internal Thermal OXidation) rate of the BOX in the final stages of Ge-condensation is hypothesised to be responsible for stopping this diffusion
Mechanism of vertical Ge nanowire nucleation on Si (111) during subeutectic annealing and growth
No full textThe direct integration of Ge nanowires with silicon is of interest in multiple applications. In this work, we describe the growth of high-quality, vertically oriented Ge nanowires on Si (111) substrates utilizing a completely sub-Au-Si-eutectic annealing and growth procedure. With all other conditions remaining identical, annealing below the Au-Si eutectic results in successful heteroepitaxial nucleation and growth of Ge nanowires on Si substrate while annealing above the Au-Si eutectic leads to randomly oriented growth. A model is presented to elucidate the effect of the annealing temperature, in which we hypothesized that sub-Au-Si-eutectic annealing leads to the formation of a single and well-oriented interface, essential to template heteroepitaxial nucleation. These results are critically dependent on substrate preparation and lead to the creation of integrated nanowire systems with a low thermal budget process
Electrodeposited Ni/Ge and germanide schottky barriers for nanoelectronics applications
No full textIn recent years metal/semiconductor Schottky barriers have found numerous applications in nanoelectronics. The work presented in this thesis focuses on the improvement of a few of the relevant devices using electrodeposition of metal on Ge for Schottky barrier fabrication. This low energy metallisation technique offers numerous advantages over the physical vapour deposition techniques. Electrical characteristics of the grown diodes show a high quality rectifying behaviour with extremely low leakage currents even on highly doped Ge. A non-Arrhenius behaviour of the temperature dependence is observed for the grown Ni/Ge diodes on lowly doped Ge that is explained by a spatial variation of the barrier heights. The inhomogeneity of the barrier hights is explained in line with an intrinsic surface states model for Ge. The understanding of the intrinsic surface states will help to create ohmic contacts for doped n-MOSFETs. NiGe were formed single phase by annealing. Results reveal that by using these high-quality germanide Schottky barriers as the source/drain, the subthreshold leakage currents of a Schottky barrier MOSFET could be minimised, in particular, due to the very low drain/body junction leakage current exhibited by the electrodeposited diodes. The Ni/Ge diodes on highly doped Ge show negative differential conductance at low temperature. This effect is attributed to the intervalley electron transfer in Ge conduction band to a low mobility valley. The results show experimentally that Schottky junctions could be used for hot electron injection in transferred-electron devices. A vertical Co/Ni/Si structure has been fabricated for spin injection and detection in Si. It is shown that the system functions electrically well although no magnetoresistance indicative of spin injection was observed
Cheng shi yang ge duan ju ji
No full text一場虛驚 : 小型歌劇 / 李建慶, 呂翎編劇 ; 張魯作曲 -- 賣糖姑娘 : 廣場秧歌劇 / 徐步編劇 ; 郭亮作曲 -- 遊京城 : 快板劇 / 李悦之編劇 -- 新態度 : 獨幕小歌劇 / 于雁軍編劇 ; 陳紫作曲.中央戲劇學院創作室編.Zhong yang xi ju xue yuan chuang zuo shi bian.Yi chang xu jing : xiao xing ge ju / Li Jianqing, Lü Ling bian ju ; Zhang Lu zuo qu -- Mai tang gu niang : guang chang yang ge ju / Xu Bu bian ju ; Guo Liang zuo qu -- You jing cheng : kuai ban ju / Li Yuezhi bian ju -- Xin tai du : du mu xiao ge ju / Yu Yanjun bian ju ; Chen Zi zuo qu
Nong cun yang ge duan ju ji
No full text夫妻過年 : 小歌劇 / 李悦之編劇 ; 郭亮作曲 -- 小倆口拜年 : 小歌劇 / 田林, 李建慶, 王命夫編劇 ; 劉鐵山, 林里作曲 -- 好軍屬 : 秧歌劇 / 賈克編劇 ; 陳紫作曲 -- 生產模範與懶漢 / 李悦之編劇 ; 邊軍作曲.中央戲劇學院創作室編.Zhong yang xi ju xue yuan chuang zuo shi bian.Fu qi guo nian : xiao ge ju / Li Yuezhi bian ju ; Guo Liang zuo qu -- Xiao liang kou bai nian : xiao ge ju / Tian Lin, Li Jianqing, Wang Mingfu bian ju ; Liu Tieshan, Lin Li zuo qu -- Hao jun shu : yang ge ju / Jia Ke bian ju ; Chen Zi zuo qu -- Sheng chan mo fan yu lan han / Li Yuezhi bian ju ; Bian Jun zuo qu
Stenothemus flavicollis Y. Yang & S. Ge 2021, sp. nov.
No full textStenothemus flavicollis Y. Yang & S. Ge sp. nov. urn:lsid:zoobank.org:act: D0040599-E6AA-4A07-ACC5-EC916A4E9D9E Figs 7E, 9C, 10D‒F, 12C Differential diagnosis It resembles S. limbatipennis, but can be distinguished by the following characters: tibiae black (orange in S. limbatipennis); aedeagus: basal piece with a large middle nodule at base of ventral side, lateroapical part of dorsal plate with a longitudinal ridge, apical parts of laterophyses narrowly separated from each other, clearly exceeding middle emargination between dorsal plates (while middle nodule small, dorsal plate not ridged at lateroapical part, apical parts of laterophyses widely separated and just reaching middle emargination in S. limbatipennis, see Yang et al. 2021: figs 3g ‒i); female abdominal sternite VIII: posterior margin rectangularly emarginate in middle, membrane behind the middle emargination triangularly bilobed at apex (while roundly emarginate in middle, membrane behind the middle emargination tapered at apex in S. limbatipennis, see Yang et al. 2021: fig. 8c); female reproductive system: diverticulum and spermatheca extremely long (relatively short in S. limbatipennis, see Yang et al. 2021: fig. 6c). Etymology The specific name is derived from the Latin ‘ flavus ’ (‘yellow’) and ‘ collum ’ (‘neck’), referring to its yellow pronotum. Material examined Holotype CHINA • ♂; Hubei, Yichang, Dalaoling Forestry Farm; 3 May 2015; T.F. Qiu leg.; MHBU HBU(E) 410029. Paratypes CHINA ‒ Hubei • 8 ♂♂, 5 ♀♀; same collection data as for holotype; MHBU HBU(E) 410030 to 410042 • 1 ♂, 1 ♀; Yichang, Dalaoling Forestry Farm; 4 May 2015; T.F. Qiu leg.; MHBU HBU(E) 410043, 410044. Description Body length (both sexes): 6.5‒9.7 mm (7.2 mm in holotype); width: 1.0‒2.0 mm (1.7 mm in holotype). Male (Fig. 9C) COLORATION. Body black, clypeus, mouthparts, antennomeres I, prothorax, coxae and femora and posterior margins of abdominal ventrites yellow. Body densely covered with short, semi-recumbent yellow pubescence. HEAD. Subquadrate, surface densely and finely punctate, each side with a smooth and rectangular impression behind antennal socket; eyes moderately protruding, head width across eyes 1.5 times wider than pronotum; terminal maxillary palpomeres long-triangular, widest in middle; antennae filiform, roughly extending to ⅔ length of elytra, antennomeres II about 2.2 times as long as wide at apices, III about 1.6 times longer than II, IV‒XI each with a smooth longitudinal impression in middle of outer edge, VII longest, XI distinctly longer than X, XI slightly thickened, pointed at apex. PRONOTUM. Subquadrate, about 1.1 times as long as wide, anterior margin arcuate, anterior angles subrounded, lateral margins nearly parallel and slightly sinuate, posterior margin slightly sinuate and narrowly bordered, posterior angles sub-rectangular, disc strongly convex on posterolateral parts, surface finely and densely punctate. ELYTRA. Nearly parallel-sided, about 3.8 times as long as humeral width, 4.8 times longer than pronotum, surface finely and densely punctate, with hardly visible longitudinal costae. AEDEAGUS (Fig. 10D‒F). Moderately swollen laterally at basal part, reduced apically in diameter; basal piece nearly as long as dorsal plate of each paramere, with a large, bifurcate conjoined middle nodule at base of ventral side; ventral processes of parameres approaching each other, short and slightly thickened apically, bent ventrally in lateral view; dorsal plates slightly longer than ventral processes, abruptly narrowed near base and approaching each other, apex acute and directed ventrally, lateroapical part with a ridge; apical parts of laterophyses depressed and separated from each other, apex acute and clearly exceeding middle emargination between dorsal plates. Female Similar to male, but body stouter than male, eyes small, less protruding, head width across eyes 1.3 times wider than pronotum, antennae shorter and roughly extending to elytral mid-length, IV‒XI without smooth longitudinal impressions; elytra about 3.4 times as long as humeral width. ABDOMINAL STERNITE VIII (Fig. 7E). Moderately narrowed posteriorly, lateroapical angles widely rounded, posterior margin widely and rectangularly emarginate in middle and feebly sinuate on both sides, behind the notch with a membrane which is sclerotized and triangularly bilobed at apex. INTERNAL ORGAN OF REPRODUCTIVE SYSTEM (Fig. 12C). Vagina elongate, with median oviduct situated at ventroapical part, vagina abruptly narrowed in apical part and extended into a short duct which diverticulum and spermathecal duct are arising from; diverticulum extremely long, about 0.99 times adult body length, evenly thinned apically, slender tube-shaped and spiral; spermathecal duct slightly long but much shorter than diverticulum; spermatheca slender tube-shaped and spiral, obviously thinner than spermathecal duct and much longer than diverticulum, with basal part extended into a short tube, at opening of accessory gland.Accessory gland thin in basal part and remainder moderately thin, obviously shorter than spermatheca. Variation within species Sometimes posterior margin of pronotum arcuate. Distribution China (Hubei).Published as part of Yang, Yuxia, Ge, Shujuan, Yang, Xingke & Liu, Haoyu, 2021, Taxonomic revision of the species of Stenothemus from Southwest China (Coleoptera, Cantharidae), with the descriptions of five new species, pp. 1-36 in European Journal of Taxonomy 757 (1) on pages 25-28, DOI: 10.5852/ejt.2021.757.1409, http://zenodo.org/record/503310
Energy and Spatial Spectral Efficiency Analysis of Random MIMO Cellular Networks
No full textIn this work, we investigate the performance of Multiple-Input Multiple-Output (MIMO) systems in Random Cellular Networks in terms of Spatial Spectral Efficiency (SSE) and Energy Efficiency (EE). In this model, M-antenna Base Stations (BS) are randomly distributed in R(exp 2) based on a Poisson Point Process (PPP). Each BS forms a cell in this Poisson-Voronoi Tessellation (PVT) random cellular network and serves K single-antenna Mobile Stations (MS). Firstly, we provide expressions for the coverage probability and the ergodic capacity using stochastic geometry techniques. Then, a Markov Chain (MC) model is considered to derive the blocking probability, SSE and EE. Simulation results reveal that a random network with multi-antenna nodes is more susceptible to interference than to noise. Although a higher path-loss exponent degrades the coverage probability in a noisy network, it results in better coverage probability in a noise-free scenario. Besides, our results show a higher SSE and EE of MIMO compared to Single-Input Single-Output (SISO), while an equal sum power constraint is considered at the BSs
The Assembly-Disassembly-Organization-Reassembly mechanism for 3D-2D-3D transformation of germanosilicate IWW zeolite
No full textThis research was part funded by EPSRC grant number EP/K025112/1. The article processing charge for this article was funded through the RCUK open access block grant.Hydrolysis of germanosilicate zeolites with the IWW structure shows two different outcomes depending on the composition of the starting materials. Ge-rich IWW (Si/Ge=3.1) is disassembled into a layered material (IPC-5P), which can be reassembled into an almost pure silica IWW on treatment with diethoxydimethylsilane. Ge-poor IWW (Si/Ge=6.4) is not completely disassembled on hydrolysis, but retains some 3D connectivity. This structure can be reassembled into IWW by incorporation of Al to fill the defects left when the Ge is removed.Peer reviewe
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