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The chelating agent triethanolamine (TEA) is introduced as an additive in the electrolyte to enhance the cycling stability of aqueous zinc-ion batteries.

With photoconductor being transferred and separated, interface contact plays a crucial role in developing composites photocatalyst. In the present work, 2D crystalline g-C3N4 (called as CCN) with 2D TiO2 nanosheets (called as TO) obtained in situ oxidized single-layered Ti3C2Tx MXene is designed by an electrostatic self-assembly technology. This CCN/TO nanosheets system with a few TiO2 nanosheets distributed to the surface is not only prolonging lifetime of photoelectron but also stimulating photogenerated carriers transferred in contact interface. The electron transfer mechanism of CCN/TO is further proved by Pt photo-deposition method. Therein, the optimal CCN-TO-0.6 exhibits excellent performance of H2 generation compared with single photocatalyst of CCN. The result shows that the crystalline g-C3N4 photocatalysts introduced TiO2 with interfacial effect favorably reduce H+ to H2 and enhance photocatalytic activity.

Development of delithiation methods with cost-efficiency and highly kinetic effectivity is of great importance for the preparation of diversified intercalation materials, mechanistic study, and lithium extraction from spent lithium-ion batteries. Electrochemical delithiation in aqueous electrolytes is low-cost, straightforward, and fast, but has been plagued by incomplete delithiation. To address this issue, we propose to add oxidation reagents, usually applied in chemical delithation, to traditional aqueous delithiation electrolyte. As a demonstration, herein, a Na2SO4 + Na2S2O8 composite aqueous electrolyte is used to obtain olivine FePO4 from the electrochemical delithiation of LiFePO4, and compared with the similar delithiation in Na2SO4 aqueous electrolyte. The delithiation goes completion in the composite electrolyte 79% faster than that in traditional electrolyte. The resulting olivine FePO4 exhibits integrity in terms of structure and electrochemical properties, with discharge specific capacity of 157.1 mAh g−1 at 0.1 C, constant voltage plateau of 3.37 V, and 98.8% capacity retention after 100 cycles, all comparable to the LiFePO4 starting material. Mechanistic studies show that Na2S2O8 promotes the electrochemical delithiation by providing acidic and chemically oxidative conditions.

In this work, vanadium particles (VP) were utilized as a novel reinforcement of AZ31 magnesium (Mg) alloy. The nanocrystalline (NC) AZ31–VP composites were prepared via mechanical milling (MM) and vacuum hot-press sintering. During the milling process, the presence of VP contributed to the cold welding and fracture mechanism, resulting in the acceleration of the milling process. Additionally, increasing the VP content accelerated the grain refinement of the matrix during the milling process. After milling for 90 h, the average grain size of AZ31-X wt % Vp (X = 5, 7.5, 10) was refined to only about 23 nm, 19 nm and 16 nm, respectively. In the meantime, VP was refined to sub-micron scale and distributed uniformly in the matrix, exhibiting excellent interfacial bonding with the matrix. After the sintering process, the average grain size of AZ31-X wt % VP (X = 5, 7.5, 10) composites still remained at the NC scale, which was mainly caused by the pinning effect of VP. Besides that, the porosity of the sintered composites was no more than 7.8%, indicating a good densification effect. As a result, there was little difference between the theoretical and real density. Compared to as-cast AZ31 Mg alloy, the microhardness of sintered AZ31-X wt % VP (X = 5, 7.5, 10) composites increased by 65%, 87% and 96%, respectively, owing to the strengthening mechanisms of grain refinement strengthening, Orowan strengthening and load-bearing effects.

In this work, nanocrystalline AZ31 magnesium alloy powders, reinforced by submicron TiB2 particles, were prepared via mechanical milling. It was found that TiB2 particles stimulated the fracture and welding of AZ31/TiB2 powders, leading to the acceleration of the milling process. Meanwhile, the TiB2 particles were refined to submicron-scale size during the milling process, and their distribution was uniform in the Mg matrix. In addition, the matrix was significantly refined during the milling process, which was also accelerated by the TiB2 particles. The formation of grain boundary segregation layers also led to the weakened TiB2 peaks in the XRD patterns during the mechanical milling. The grain sizes of AZ31–2.5 wt % TiB2, AZ31–5 wt % TiB2 and AZ31–10 wt % TiB2 powders were refined to 53 nm, 37 nm and 23 nm, respectively, after milling for 110 h. Under the combined effect of the nanocrystalline matrix and the well-dispersed submicron TiB2 particles, the AZ31/TiB2 composites exhibited excellent micro-hardness. For the AZ31–10 wt % TiB2 composite, the micro-hardness was enhanced to 153 HV0.5.

The microstructure evolution of a typical nickel-based superalloy was studied in the strain range of 0.1–0.9 at 1110 °C/0.01 s−1 by using the electron backscattered diffraction technique. It was found that the evolution of recrystallized microstructures, grain boundary characteristics, and textures was closely related to strain level. With the increasing strain level, the fraction of equiaxed dynamic recrystallization (DRX) grains increased significantly at the expense of the large non-recrystallized grains, and there was a decrease in total low angle grain boundaries fraction and a simultaneous increase in the fraction of high angle grain boundaries. In addition, the occurrence of DRX promoted the formation of Σ3 boundaries, and the coherent Σ3 boundaries were much easier to form at the strain above 0.5. On the other hand, component of the textures became stronger with the increasing strains, and the lack of orientations can also be observed in the textures at high strains above 0.7.

The mechanism underlying the crowding effects that assist the condensation process by multivalent cations under confinement is not yet reported. Based on the strong correlation model, Monte Carlo simulation was implemented to detect the crowding effects on DNA condensation within a capsule-like space, and its geometry controlled by the aspect ratio. With the addition of crowders, the condensed conformations confined within the spherical space (aspect ratio is 1) become more compact than those without crowders. The DNA-condensed conformations undergo a transition from the initial random coil structure to toroid structure, followed by the extended rod-like structure, and finally to totally compacted structure. The critical volume fraction corresponding to the transition from the rod-like structure to totally compacted structure pertained to the crowder size proportionally. Moreover, the critical volume fraction corresponding to the phase transition strongly depends on the confinement geometry, the critical volume fraction for the case with constant radius is inversely proportional to the aspect ratio. Conversely, the case with constant cylinder length showed that the critical volume fraction is proportional to the aspect ratio. These phenomena are consistent with their corresponding phase diagram re-expressed in the space of volume fraction and aspect ratio. The effects of confinement geometry and crowder size on the response of DNA condensation to crowding are elucidated and generalized into the space diagram in the space of aspect ratio and crowder size. When the aspect ratio less than 1.6 and the crowder size larger than 2.0 nm or when the aspect ratio ≥ 1.6 and the crowder size larger than the critical d c ∗ , the DNA conformation undergo the transition from the initial random coil structure to toroid structure, followed by totally compacted structure; when the aspect ratio ≥ 1.6 and the crowder size ≤ d c ∗ , the DNA condensed conformations will be condensed further from the totally compacted structure to the extended rod-like structure. Furthermore, the transition from the totally compacted structure to the extended rod-like structure is entirely due to the crowder size and the confinement geometry between the de Gennes and Odijk regimes.

The paper presents a systematical simulation study of the influence of gradient doping of both emitter and back surface field layer on the photovoltaic (PV) performances of TCO/a-Si:H(p)/a-Si:H(i)/c-Si(n)/a-Si:H(n+)/TCO/Ag bifacial structure heterojunction with intrinsic thin layer (HIT) solar cells using AFORS-HET software simulation package. The gradient doping instead of uniform doping for emitter can promote the PV performance due to the presence of an additional electric field coming from the gradient doping, while the gradient doping of back surface field layer has negligible effect or negative influence on the cell performance compared to uniform doping, which can be explained by the varied energy band diagrams near the back junction interface. A final efficiency of 25.75% has been realized by using gradient doping of emitter with the same total doping amount as that of uniform doping case and uniform doping of back surface field layer for n-type bifacial HIT solar cells. This study can offer guidance on how to improve HIT solar cell efficiency beyond the world record value in experiment and how to achieve higher efficiency in mass production of HIT solar cells.

Deep insight into the crystallization mechanism of amorphous silicon is of theoretical and technological significance for the preparation of high-quality microcrystalline/polycrystalline silicon. In this work, we intensively compare the present two plasma-involved routes, i.e., the direct deposition and recrystallization of precursor amorphous silicon (a-Si) films, to fabricate microcrystalline silicon. Both the directly deposited and recrystallized samples show multi-layered structures as revealed by electronic microscopy. High-density hydrogen plasma involved recrystallization process, which is mediated by the hydrogen diffusion into the deep region of the precursor a-Si film, displays significantly different nucleation configuration, interface properties, and crystallite shape. The underlying mechanisms are analyzed in combination with the interplay of high-density plasma and growing or treated surface.

Nanocrystalline AZ61 powders, dispersed with submicron/nanometer Ti particulates, were mechanically milled and a comparative study on thermal stability and mechanical properties was performed. After mechanical milling, Ti dispersions were cracked to submicron/nanometer particulates and Mg grains were refined to nanocrystalline. As illustrated by high-resolution transmission electron microscopy, coherent lattice and semi-coherent lattice interfaces between magnesium and titanium were achieved. Based on high angle annular dark field and corresponding energy dispersive spectrometer maps, Al dissolved into Ti particulates after mechanical milling. Moreover, the emergence of Ti3Al phase was verified by X-ray diffraction during mechanical milling and heat treatment. According to heat treatment results, this nanocrystalline magnesium composite exhibits a preeminent thermal stability among nano-structured magnesium alloys. After annealed at 673 K for 600 min, the composite still remained nanocrystalline with average grain size being 68.6 nm. Due to such microstructure, the composite revealed prominent mechanical property with the hardness being 146.6 HV. Simultaneously, the hardness of annealed composite remained high, with the value being 134.7 HV, which could ascribe to the excellent thermal stability.

Being a key issue in the research and fabrication of silicon heterojunction (SHJ) solar cells, crystalline silicon (c-Si) surface passivation is theoretically and technologically intricate due to its complicate dependence on plasma characteristics, material properties, and plasma-material interactions. Here amorphous silicon (a-Si:H) grown by a planar inductively coupled plasma (ICP) reactor working under different antenna-substrate distances of d was used for the surface passivation of low-resistivity p-type c-Si. It is found that the microstructures (i.e., the crystallinity, Si-H bonding configuration etc.) and passivation function on c-Si of the deposited a-Si:H were profoundly influenced by the parameter of d, which primarily determines the types of growing precursors of SiHn/H contributing to the film growth and the interaction between the plasma and growing surface. c-Si surface passivation is analyzed in terms of the d-dependent a-Si:H properties and plasma characteristics. The controlling of radical types and ion bombardment on the growing surface through adjusting parameter d is emphasized.

The functional coatings play a critical role in many fields. To obtain difunctional composite coatings with low infrared emissivity and electrostatic dissipation (ESD) property, the composite coatings reinforced by aluminum-doped zinc oxide (AZO) and ESD carbonaceous fiber (CF) hybrid pigments were prepared, which were characterized by X-ray diffraction, scanning electron microscopy, infrared emissometer and insulation resistance tester. The effects of Al doping ratio of AZO, pigment adding amount and pigment type on the infrared emissivity and surface resistivity of the composite coating have been studied. The results confirmed that AZO of 7at.% doping concentration has lower infrared emissivity, and the infrared emissivity of AZO and CF coatings decreases with the increase of filler content. When AZO and CF are mixed at 1:1, the surface resistivity of the coating is 6380 Ω, which is much lower than that of any single pigment coating. Their synergy effect was contributed to form a continuous conductive path in the coating, enhance the tunnel current and obtain low surface resistivity for electrostatic dissipation. This work provides a new strategy for developing difunctional composite coatings with low infrared emissivity and electrostatic dissipation property.

Recently plasmonic effect has attracted tremendous interests due to its ability of light trapping and improving the photovoltaic performances of solar cells. In this letter, we propose a solution method based fabrication route of Ag plasmons and realize a pronounced optical gain in ZnO:Al (AZO) thin film, which is strongly beneficial to harvest incident sunlight in thin film solar cells. Processing parameters, such as spinning speed, coating times and post-annealing temperature, could be regulated to optimize the plasmon effects of silver particles. The reflectance of silver particles coated AZO (Ag/AZO) is reduced by ~18%, and the transmittance is enhanced by ~40% simultaneously. The underlying mechanisms are discussed in combination with the microstructures of the silver particles.

Mechanical milling was used to prepare nanocrystalline AZ31 magnesium (Mg) alloy with titanium (Ti) addition. During milling, the crystallite size of the AZ31 Mg matrix decreased steadily with the increase of milling time. After milling for 110 h, the crystallite size of the Mg phase of the alloy with 18 wt.% and 27 wt.% Ti additions was refined to 86 nm and 66 nm respectively, leading to the formation of a nanocrystalline Mg matrix microstructure. Meanwhile, the size of Ti particles added in the alloy also decreased gradually with the increase of milling time, and the Ti dispersions presented a positive effect on the refinement of the Mg matrix grains. By milling for 110 h, the average size of Ti particles was refined to less than 1 μm in the AZ31 Mg alloy with 18 wt.% Ti addition. After mechanical milling, the as-milled powders were cold pressed into green compacts, and the mechanical properties were characterized by Vickers' hardness and uni-axial compressive tests. It was found that the micro-hardness of mechanically milled AZ31 Mg alloy with 27 wt.% Ti addition reached about 147 Hv, which was almost three times larger than that of the as-received AZ31 Mg alloy. Meanwhile, the yield strength of mechanically milled Ti-added AZ31 Mg alloy was seen to be as high as 293 MPa at room temperature and 60 MPa at 300 °C, respectively.

The influence of electropulsing treatment (EPT) parameters on the static recrystallization (SRX) microstructure in a cold-deformed Ni-based superalloy was investigated. During EPT, both the volume fraction of SRX grains and the average grain size increased with the increasing EPT temperature, which was attributed to the thermal effect and athermal effect induced by EPT. The mobility of SRX grain boundaries was promoted at the higher temperature due to the thermal effect, while the nucleation rate would be increased by EPT through decreasing the thermodynamic barrier. The formation of parallel dislocations caused by electron wind force could also play an indirect role in promoting SRX process. Moreover, the volume fraction of SRX grains increased significantly with the extension of EPT time at 700 &deg, C, while the EPT time had a trivial effect on the average grain size. In addition, the sufficient deformation was essential to the occurrence of SRX behavior during EPT, and the localized Joule heating effect could promote the SRX behavior in the samples with the larger strains. Besides that, the influence of twining and carbides on the SRX behaviors was also investigated.

Evolution of grain structure and grain boundary character distribution in a cold-deformed Ni-based superalloy during the electropulsing treatment (EPT) was investigated by EBSD technique. Compared with the conventional heat treatments (CHT), the nucleation and growth of SRX grains were significantly accelerated by EPT, which was mainly attributed to the high mobility of dislocations and solute atoms, and the efficient energy transfer under the effect of EPT. Especially, with the introduction of electric current, the activation energy of dislocation motion could be reduced by generating additional energy near the dislocation line, which made the motion of dislocation easy to start. The dislocations would also be easy to move in the form of slipping and climbing, under the effect of electron wind force. On the other hand, most of Σ3 boundaries were newly formed through growth accidents in the form of coherent Σ3 boundaries during EPT, and the mutual interactions between different Σ3n (n = 1, 2, 3) boundaries were rather limited. In addition, EPT could indirectly promote the formation of Σ3 boundaries by accelerating the SRX process, but the formation of Σ9 and Σ27 boundaries was inhibited at the temperatures higher than 700 °C. Moreover, the connectivity of random boundaries in the cold-deformed alloy treated by EPT was also discussed.

The method of mechanical milling was applied to synthesize nanocrystalline MgxTi100 − x (x = 95, 90, 85) composite powders. The results reveal that mechanical milling is an effective method for preparing Mg–Ti composite powders, which consist of nanocrystalline Mg matrix and fine dispersed Ti particles. Moreover, the microstructure evolution and morphology of the as-milled powders were observed, and the corresponding mechanisms were also discussed. After milling for 60 h, the crystallite size of the matrix Mg in MgxTi100 − x (x = 95, 90, 85) composite powders was refined to 105 nm, 84 nm, and 76 nm, respectively. Meanwhile, the average size of the dispersed Ti particles in MgxTi100 − x (x = 90) composite powders was refined to about 1 μm. Based on the XRD data, the solid solubility of Ti in Mg was calculated by using the Vegard's law. For all these Mg–Ti composite powders, the solid solubility of Ti in Mg seemed to be closely related with the milling time and the content of Ti. In the 60 h-milled MgxTi100 − x (x = 95, 90, 85) composite powders, the solid solubility of Ti in Mg was estimated to be 0.56 at.%, 1.32 at.% and 2.35 at.%, respectively.

The surface properties of photocatalysts strongly affect interfacial catalytic reaction and determine photocatalytic activity. In this work, surface-modified graphitic carbon nitride (g-C3N4) nanosheets were prepared via plasma treatment in H2, H2-CH4, and Ar atmosphere. Hydrogenated g-C3N4 nanosheets with hydrophilic group C-N-H, defect state, and exfoliated morphology were obtained via treating g-C3N4 nanosheets with H2 plasma at room temperature. The hydrogenated g-C3N4 nanosheets possessed the improved photocatalytic activity for hydrogen evolution, and the rate of hydrogen evolution exceeded that of pristine g-C3N4 by a factor of 4.8. Photocatalytic activity improvement is due to the introduction of hydrophilic group C-N-H, defect states, and exfoliated nanosheet morphology. Hydrophilic functional group of C-N-H can effectively capture water molecules. Defect states generated via plasma treatment acted as a capture center to suppress carrier recombination and transfer the trapped electrons to the adsorbed water molecules. Exfoliated nanosheet morphology provided a large number of active sites for catalytic reaction. Optical emission spectroscopy supported the introduction of hydrogen species during H2 plasma treatment of g-C3N4. First-principle density functional theory calculations confirmed the enhanced adsorption capacity of hydrogenated g-C3N4 for water molecules. The mechanism of enhanced photocatalytic H2-production activity was further proposed.

Author(s): Chen, S; Zhou, H; Ye, X; Chen, Z; Zhao, J; Das, S; Klewe, C; Zhang, L; Lupi, E; Shafer, P; Arenholz, E; Jin, D; Huang, H; Lu, Y; Li, X; Wu, M; Ke, S; Xu, H; Zeng, X; Huang, C; Martin, LW; Chen, L | Abstract: The ability to tailor a new crystalline structure and associated functionalities with a variety of stimuli is one of the key issues in material design. Developing synthetic routes to functional materials with partially absorbed nonmetallic elements (i.e., hydrogen and nitrogen) can open up more possibilities for preparing novel families of electronically active oxide compounds. Fast and reversible uptake and release of hydrogen in epitaxial ABO3 manganite films through an adapted low-frequency inductively coupled plasma technology is introduced. Compared with traditional dopants of metallic cations, the plasma-assisted hydrogen implantations not only produce reversibly structural transformations from pristine perovskite (PV) phase to a newly found protonation-driven brownmillerite one but also regulate remarkably different electronic properties driving the material from a ferromagnetic metal to a weakly ferromagnetic insulator for a range of manganite (La1−xSrxMnO3) thin films. Moreover, a reversible perovskite-brownmillerite-perovskite transition is achieved at a relatively low temperature (T ≤ 350 °C), enabling multifunctional modulations for integrated electronic systems. The fast, low-temperature control of structural and electronic properties by the facile hydrogenation/dehydrogenation treatment substantially widens the space for exploring new possibilities of novel properties in proton-based multifunctional materials.

The performance of a solid-state planar nano-diode, namely self-switching diode (SSD), is improved by depositing a 100-nm-thick SiNx film with high dielectric constant (high-k) into the insulating nano-trenches. The SiNx film grown by using plasma-enhanced chemical vapour deposition (PECVD) can enhance the electric field coupling over the trenches and thus increase the accumulated charges for field effect. In this case, the current-voltage nonlinearity is improved significantly and the responsivity of high frequency rectification is also increased by a factor of almost one order up to 100 GHz. In addition, compared to the device without SiNx coating, the low frequency noise of the proposed diode is suppressed dramatically. The improved responsivity and noise-equivalent power (NEP) of 11 SSDs in parallel with SiNx coating are 110 V/W at 50 GHz and 180 pW/Hz1/2 ,which are comparable to the state-of-the-art data of reported SSD arrays.

The electronic structure, and optical and mechanical properties of gamma- Si 3 N 4 are calculated by means of the plane-wave pseudo-potential method (PWP) with generalized gradient approximation (GGA) and local density approximation (LDA). The calculated values are in good agreement with experimental results. A comparative investigation reveals that the band gap calculated by GGA agrees better with the experimental value than by the other methods, while the calculated bulk modulus by LDA is comparable with that by the method of orthogonalized linear combinations of atomic orbitals (OLCAO). Our results indicate that a satisfactory calculation of the structures and properties of gamma- Si 3 N 4 could be achieved by combining GGA and LDA methods.

This paper investigates a low damage reactive ion etch (RIE) process to make thin silicon nitride sidewall spacers for the fabrication of self-aligned sub-100nm gate length III-V metal-oxide-semiconductor field-effect-transistors (MOSFETs). Self-alignment is essential to minimize the contribution to the parasitic series source/drain resistance (RSD) from the access region between the ohmic contact and the gate, whilst retaining the overall electrostatic integrity of the device. In this work, a blanket Si"3N"4 was deposited by room temperature inductively coupled plasma chemical vapour deposition (ICP-CVD) and etched by reactive ion etching in a SF"6/N"2 based chemistry. Conditions were optimised to ensure low damage to the underlying device layer stack. This process has successfully produced thin Si"3N"4 spacers for fabricating self-aligned GaAs MOSFETs. The sheet resistance of III-V MOSFET materials was monitored as a function of etch parameters to assess the impact of damage related effects on the electronic characteristics of the underlying material. The etching profile and the sheet resistance of the device layer structures were characterised by using scanning electronic microscope (SEM) and sonogage, respectively.

Two methods for high resolution dry etching of permalloy (NiFe) and iron (Fe) nanostructures are presented and discussed. The first involves the use of carbon monoxide (CO) and ammonia (NH"3) as etching gases, the second uses methane (CH"4), hydrogen (H"2) and oxygen (O"2). In both etching processes volatile metallo-organic compounds are the resulting reaction products. The patterned and dry etched thin films were observed with SEM and TEM to study the quality of each of the two processes. It is found that the CO/NH"3 process yields higher etch rates, higher selectively with respect to the SiN mask used, and less redeposition than the CH"4/H"2/O"2 process.

This paper investigates the reactive ion etching of Ga"xGd"yO"z, a device quality high-k gate oxide for the fabrication of III-V metal-oxide-semiconductor field-effect-transistors (MOSFETs) based on high mobility channel device layer structures. The etching of Ga"xGd"yO"z (GGO) was performed in an SRS System ET340 with a CH"4/H"2/O"2 based chemistry The GGO high-k gate stacks for GaAs MOSFETs were grown by molecular beam epitaxy in a dual-chamber system. Etching profile was characterised by SEM using a wet chemical HCl/HF/H"2O decoration etch to assist layer identification. The effects of etching gas, RF power, and duration of CH"4/H"2 and O"2 gas cycles on etch process were investigated.

This paper investigates reactive ion etching (RIE) of sputtered tungsten films, a suitable candidate for gate metallization in compound semiconductor based high mobility channel devices, with the aim of developing a detailed understanding of the effects of etching parameters vital to reducing etch-induced damage and improving etching performance, yield, uniformity and repeatability. An Oxford Instruments PlasmaLab System 100 RIE etch tool and SF"6 based chemistry in combination with various functional gases, such as N"2, O"2 and CHF"3 was used in this study. To evaluate plasma-induced damage caused by the RIE process, GaAs based HEMT (high electron mobility transistor) type layer structures with channels buried 18nm from the surface were grown by molecular beam epitaxy (MBE). Subsequently, Van der Pauw structures were fabricated on this material and used to assess the effects of the RIE process on sheet resistivity, carrier concentration and mobility in the device channel. Etched tungsten line widths down to 25nm were obtained by electron beam lithography with Sumitomo NEB31 resist as an etch mask. The effects of etching gases of SF"6+N"2, SF"6+O"2, and SF"6+CHF"3, RF power, and etching temperature on etching profile and etching-induced damage were investigated.

The interfacial microstructure and properties of brazed joints of a Ti 3 Al-based alloy were investigated in this paper to meet the requirements of the use of Ti 3 Al-based alloy in the aeronautic and space industries. The effects of different brazing fillers on the interfacial microstructure and shear strength were studied. The relationship between brazing parameters and shear strength of the joints was discussed, and the optimum brazing parameters were obtained. The brazed joints were qualitatively and quantitatively analyzed by means of EPMA, SEM and XRD. The results showed that using a AgCuZn brazing filler, TiCu, Ti(Cu,Al) 2 and Ag[s,s] were formed, the shear strength of the joint was decreased because of the formation of TiCu and Ti(Cu,Al) 2 ; using a CuP brazing filler, Cu 3 P, TiCu and Cu[s,s] were formed at the interface of the joint, the former two intermetallic compounds decreased the shear strength. The analysis also indicated that using the TiZrNiCu brazing filler, the optimum parameters were temperature T =1323 K, joining time t =5 min, and the maximum shear strength was 259.6 MPa. For the AgCuZn brazing filler, the optimum parameters were joining temperature T =1073 K, joining time t =5 min, and the maximum shear strength was 165.4 MPa. To the CuP brazing filler, the optimum parameters were joining temperature T =1223 K, joining time t =5 min, and the maximum shear strength is 98.6 MPa. Consulting the results of P. He, J.C. Feng and H. Zhou [Microstructure and strength of brazed joints of Ti 3 Al-base alloy with NiCrSiB, Mater. Charact., 52(8) (2004) 309–318], relative to the other brazing fillers, TiZrNiCu is the optimum brazing filler for brazing Ti 3 Al-based alloy.

Brazing of Ti 3 Al alloys with the filler metal TiZrNiCu was carried out at 1173–1373 K for 60–1200 s. The relationship of brazing parameters and shear strength of the joints was discussed and the optimum brazing parameters were obtained. When products are brazed, the optimum brazing parameters are as follows: brazing temperature is 1273–1323 K, brazing time is 250–300 s. The maximum shear strength of the joint is 250–260 MPa. Four kinds of reaction products were observed to have formed during the brazing of Ti 3 Al alloys with the filler metal TiZrNiCu, namely Ti 2 Ni + TiCu intermetallic compounds formed close to the Ti 3 Al alloy. TiNi 2 Cu intermetallic compounds layer formed between Ti 2 Ni + TiCu intermetallic compounds and the filler metal and a Ti[s,s] (here s,s means super saturation) solid solution formed with the dispersed TiNi 2 Cu in the middle of the joint. The interfacial structure of brazed Ti 3 Al alloys joints with the filler metal TiZrNiCu is Ti 3 Al/Ti 2 Ni + TiCu/TiNi 2 Cu/Ti[s,s] solid solution + TiNi 2 Cu/TiNi 2 Cu/TiCu + Ti 2 Ni/Ti 3 Al and this structure will not change with brazing time once it forms. The formation of over many intermetallic compounds Ti 2 Ni + TiCu + TiNi 2 Cu results in embrittlement of the joint and poor joint properties. The thickness of Ti 2 Ni + TiCu + TiNi 2 Cu intermetallic compounds increases with brazing time according to a parabolic law. The activation energy Q and the growth velocity K 0 of the reaction layer Ti 2 Ni + TiCu + TiNi 2 Cu in the brazed joints of Ti 3 Al alloys with the filler metal TiZrNiCu are 261 kJ/mol and 0.0434 mm 2 /s, respectively and the growth formula was y 2 = 0.0434 exp(−31392.83/ T ) t . Careful control of the growth of the reaction layer Ti 2 Ni + TiCu + TiNi 2 Cu can influence the final joint strength.

Brazing of Ti 3 Al alloys with the filler metal NiCrSiB was carried out at 1273–1373 K for 60–1800 s. The relationship of brazing parameters and shear strength of the joints was discussed, and the optimum brazing parameters were obtained. When products are brazed, the optimum brazing parameters are as follows: brazing temperature is 1323–1373 K, brazing time is 250–300 s. The maximum shear strength of the joint is 240–250 MPa. Three kinds of reaction products were observed to have formed during the brazing of Ti 3 Al alloys with the filler metal NiCrSiB, namely, TiAl 3 (TiB 2 ) intermetallic compounds formed close to the Ti 3 Al alloy. TiAl 3 +AlNi 2 Ti (TiB 2 ) intermetallic compounds layer formed between TiAl 3 (TiB 2 ) intermetallic compounds and the filler metal and a Ni[s,s] solid solution formed in the middle of the joint. The interfacial structure of brazed Ti 3 Al alloy joints with the filler metal NiCrSiB is Ti 3 Al/TiAl 3 (TiB 2 )/TiAl 3 +AlNi 2 Ti (TiB 2 )/Ni[s,s] solid solution/TiAl 3 +AlNi 2 Ti (TiB 2 )/TiAl 3 (TiB 2 )/Ti 3 Al, and this structure will not change with brazing time once it forms. The formation of over many intermetallic compounds TiAl 3 +AlNi 2 Ti (TiB 2 ) results in embrittlement of the joint and poor joint properties. The thickness of TiAl 3 +AlNi 2 Ti (TiB 2 ) intermetallic compounds increases with brazing time according to a parabolic law. The activation energy Q and the growth velocity K 0 of the reaction layer TiAl 3 +AlNi 2 Ti (TiB 2 ) in the brazed joints of Ti 3 Al alloys with the filler metal NiCrSiB are 349 kJ/mol and 24.02 mm 2 /s, respectively, and the growth formula was y 2 =24.04exp(−41977.39/ T ) t . Careful control of the growth of the reaction layer TiAl 3 +AlNi 2 Ti (TiB 2 ) can influence the final joint strength.

The low-temperature rapid solid phase crystallization route of amorphous silicon is fundamentally and technologically significant. Micrometer thick hydrogenated amorphous silicon (a-Si:H) films were exposed to a low-frequency inductively coupled hydrogen plasma under a low substrate temperature of 300 °C. The plasma treated a-Si:H was completely crystallized within half an hour. The evolution of microstructures, optical and electric properties with respect to plasma exposure duration deterministically demonstrates that the present low-temperature rapid crystallization process enables the controllable phase transition from amorphous to nanocrystalline (nc) silicon. The crystallization mechanism is discussed in terms of the unique characteristics of low-frequency inductively coupled plasma (LFICP) and the LFICP-grown precursor a-Si:H film itself. The crucial role of hydrogen atoms in the phase transition is also discussed.

We present a Hall magnetometer combined with a conventional atomic force microscope (AFM) tip. The Hall nanosensor AFM probe is fabricated in bismuth using direct-wire electron-beam nanolithography and silicon micromachining. The magnetometer is integrated into a conventional force microscope silicon cantilever which permits reliable control of the sensor-sample distance. The magnetic sensor is situated at the end of a sharp AFM allowing good access to the specimen and providing high resolution simultaneous topographic images. Since the sensors are defined lithograpically, the size and shape of sensors are well controlled and reproducible. We present the results of magnetic field imaging using this probe demonstrating quantitative magnetic field measurement and good spatial resolution.

This paper investigates the reactive ion etching (RIE) of Ga"xGd"yO"z, a device quality [email protected] gate oxide for a low resistance ohmic contact realisation in fabricating III-V metal-oxide semiconductor field-effect-transistors (MOSFETs) based on high mobility channel device layer structures. The etching of Ga"xGd"yO"z (GGO) was performed in an Oxford Instrument PlasmaLab System 100 RIE etcher with a SiCl"4 based chemistry. The GGO [email protected] gate stacks for GaAs MOSFETs were grown by Molecular Beam Epitaxy (MBE) in a dual-chamber system. Etching profile was characterised by AFM, SEM and TEM methods. The effects of usual etching conditions, such as RF power and chamber pressure on etch process were investigated. Based on the etching process, a low resistance ohmic contact has been realised as well, which has successfully been used in the fabrication of GaAs MOSFETs.

We present recent work in which direct-write electron-beam lithography has been used to fabricate near-field optical, thermal and magnetic sensors. Key fabrication issues affecting the performance of these probes are discussed and recent fabrication results are presented.

This paper presents a low damage, ion implantation mask removal process where the ion implantation mask, consisting of photoresist and Si"3N"4 deposited by room temperature ICP-CVD (inductively coupled plasma chemical vapour deposition), has been successfully removed through combining ICP (inductively coupled plasma) O"2 plasma ashing and SF"6/O"2 reactive ion etching (RIE) of the Si"3N"4. The process leaves a clean, smooth post-etching surface with rms roughness of less than 1nm, on a device quality, high-@k Ga"xGd"yO"z (GGO) oxide layer for the fabrication of III-V metal-oxide-semiconductor field-effect-transistors (MOSFETs). Equally importantly, no etch induced damage occurs in the underlying high mobility III-V semiconductor layers. The post-etched GGO surface roughness and electrical transport properties of the underlying device layer structures were characterised by atomic force microscopy (AFM) and sonogage, respectively.

This paper investigates high resolution, low damage dry etching of tungsten, a suitable candidate for gate metallization in compound semiconductor based high mobility channel device, by using a Surface Technology Systems Ltd. (STS) inductively coupled plasma (ICP) etching system with SF"6 and C"4F"8 process gases. Low stress tungsten films with thicknesses in the range 100-200nm were deposited on GaAs substrates for the etching tests using a Plassys MP900S sputter coater. To evaluate the plasma-induced damage in the ICP etching process, GaAs based high electron mobility transistor (HEMT) type layer structures with channels buried less than 20nm from the surface, were grown by molecular beam epitaxy (MBE). Subsequently, Van der Pauw (VdP) structures were fabricated to enable determination of the impact of the etching on room temperature sheet resistivity, carrier concentration and electron mobility. The investigation of the effect of various etching parameters on the profile, minimum feature size and electrical damage has led to a low damage ICP etching process with minimum feature size of 25nm, which is suitable for the fabrication of compound semiconductor based high mobility channel devices.

This paper describes a robust process for the fabrication of highly doped Silicon-On-Insulator nanowires and devices. The process uses electron-beam lithography, lowdamage dry etch and controlled thermal oxidation to deliver consistent, reproducible and reliably nanowires of nominal widths from 100 nm down to sub-5 nm etched to a depth of 55 nm in silicon. Initial electrical measurements indicate metallic behavior for the widest wires and below a particular width, the wires become depleted showing electrical behaviour consistent with Coulomb blockade at room temperature.

This article describes a process flow that has enabled the first demonstration of functional, fully self-aligned 100nm enhancement mode GaAs metal-oxide-semiconductor field-effect transistors (MOSFETs) with GaxGdyOz as high-κ dielectric, Pt∕W as metal gate stack, and SiN as sidewall spacers. The flow uses blanket metal and dielectric deposition and low damage dry etch modules. As a consequence, no critical dimension lift-off processes are required. Encouraging data are presented for 100nm gate length devices including threshold voltage of 0.32V, making these the shortest, fully self-aligned gate length enhancement mode III-V MOSFETs reported to date. This work is a significant step forward to the demonstration of high performance “siliconlike” III-V MOSFETs.