Ni Film Thickness Research Articles

Effects of Ni Film Thickness on the Properties of Ni-Based Silicides Formed on Both Highly Doped n- and p-Si Substrate

Ni-based silicides continue to play an indispensable role during the remarkable development of microelectronics. In this work, on both highly boron (B)-doped n-Si and phosphorus (P)-doped p-Si substrate, the effects of the thickness of initial Ni films on Ni-based silicides properties are investigated comprehensively. Ni films with varying thicknesses from 1–10 nm are deposited followed by rapid thermal annealing (RTP) to form Ni-based silicides. Sheet resistance, phase identity, thermal stability and dopant redistribution are versatilely characterized by four-point probe, X-ray diffraction (XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Secondary Ion Mass Spectroscopy (SIMS). It is found that the dopants tend to segregate at silicides/Si interface when the thickness of Ni films is 3 nm or less, which is paramount beneficial to reduce effective Schottky barrier heights (SBHs) thus lowering specific contact resistivity (ρc).

Magnetic anisotropy switching induced by shape memory effect in NiTi/Ni bilayer

Strain modulation during a two-way shape memory effect (TWSME) in a sputtered nitinol NiTi is used to reliably induce and switch by 90° a uniaxial magnetic anisotropy of a 20 nm thick Ni film during the thermal cycle from 300 K to 400 K. NiTi strain and its distribution are carefully measured by digital image correlation during tensile prestrain and subsequent temperature cycles in order to compare with Ni strain extracted from the magnetometry measurement and from transmission electron microscopy. In a NiTi/Ni bilayer, a variation of 2.7% strain in NiTi during the TWSME generates 1.3% strain in Ni, which results in a transition from −2 × 104 J/m3 in-plane magnetic anisotropy to +1 × 105 J/m3. Such a composite system offers a way to timely ease writability while maintaining high thermal stability at rest in magnetic media.

Study of adhesion characteristic of a surface alloy formed by a low-energy high-current electron beam

In the present work, the adhesive strength of the surface alloy with different transition layer thickness was measured. A Ni-Cu surface alloy is formed using successive operations of Ni film deposition followed by mixing in a melted phase with the Cu substrate by a low-energy, high-current electron beam (LEHCEB). A different thickness of the transition layer was obtained by varying the thickness of Ni film deposited during the formation of the surface alloy. The study includes characterization of formed Ni-Cu surface alloys by scanning electron microscopy, in-depth elements distribution and scratch test. The results obtained showed correlation with thickness of the transition layer and adhesive strength of the surface alloy.

Hierarchical Structure Including Nanoscale Passages By Using Wet-Etching of Nickel Thin Films in Lamellae Layers for Bio-Sensors Applications

In recent years, research for surface hierarchical structures for chemical sensor and bio-sensor devices applications has been highlighted owing to their relatively large ratio of surface-area compared to the volume. Especially, the hierarchical micro-nanostructures (organization of the nanostructure within the microstructure) including nanoscale passages have been intensively studied, because nanoscale passages are necessary for single-molecule DNA sequencing. In order to realize a hierarchical micro-nanostructure, the fabrication process for micro- and nano-scale structures should be applied together, controlling each pattern size precisely. Therefore, the properties of lateral Ni film etching by TFB etchant at room temperature were investigated by using samples with patterned lamellae layers consist of Ni, Al2O3, and SiO2 for fabricating hierarchical structures for the fabrication of hierarchical structure including nanoscale passages. Lateral etching length was increased with increasing etching time, despite of the difficult passage through nanoscale passage in lamellae layers. However, higher etching rate (2.1 nm/s) was observed in lower Ni film, which has contact with SiO2 and Al2O3 layers, compared to that (1.6 nm/s) of upper Ni film, which has contact with only Al2O3, due to stronger wetting property of SiO2, inducing easier penetration of etchant into nanoscale passage between surrounding layers. Moreover, the influence of Ni film thickness on lateral etching characteristics was also investigated. In this presentation, the fabrication process based on lateral Ni film etching in lamellae layers by liquid etchant at room temperature will be presented systematically for bio-sensor applications.

Thermal stability study of Ni–Si silicide films on Ni/4H-SiC contact by in-situ temperature-dependent sheet resistance measurement

We investigate the Ni–Si film silicidation process on 4H-SiC and Si substrates and compare the thermal stability of the films grown on each substrate. The Ni–Si films were subjected to rapid thermal annealing (RTA) in the temperature range 575 °C–975 °C for 90 s, and their thermal stability was characterized by in-situ temperature-dependent sheet resistance measurements at temperatures of 25 °C–550 °C. The sheet resistance of a 40 nm thick Ni film was observed to increase sharply above 330 °C in the Ni/Si (100) interface, but slightly decrease at approximately 480 °C in the Ni/4H-SiC interface. The thermal stability of the films was found to be significantly dependent on the RTA temperature. Thermally stable Ni–Si silicide films with excellent Ohmic properties (no hysteresis behavior) can be obtained on 4H-SiC substrates at RTA temperatures of 925 °C–975 °C and can used for application in MOSFET devices.

Oxygen Evolution Reaction at IrO2/Ir(Ni) Film Electrodes Prepared by Galvanic Replacement and Anodization: Effect of Precursor Ni Film Thickness.

IrO2/Ir(Ni) film electrodes of variable Ni content have been prepared via a galvanic replacement method, whereby surface layers of pre-deposited Ni are replaced by Ir, followed by electrochemical anodization. Electrodeposition of Ni on a glassy carbon electrode support has been carried out at constant potential and the charge of electrodeposited Ni controlled so as to investigate the effect of precursor Ni layer thickness on the electrocatalytic activity of the corresponding IrO2/Ir(Ni)/GC electrodes for the oxygen evolution reaction (OER). After their preparation, these electrodes were characterized by microscopic (SEM) and spectroscopic (EDS, XPS) techniques, revealing the formation of Ir deposits on the Ni support and a thin IrO2 layer on their surfaces. To determine the electroactive surface area of the IrO2 coatings, cyclic voltammograms were recorded in the potential range between hydrogen and oxygen evolution and the charge under the anodic part of the curves, corresponding to Ir surface oxide formation, served as an indicator of the quantity of active IrO2 in the film. The electrocatalytic activity of the coatings for OER was investigated by current–potential curves under steady state conditions, revealing that the catalysts prepared from thinner Ni films exhibited enhanced electrocatalytic performance.

Pre-Coated Fe–Ni Film to Promote Low-Pressure Carburizing of 14Cr14Co13Mo4 Steel

Case-hardening 14Cr14Co13Mo4 martensitic stainless steel needs to be carburized to improve surface performance. Low-pressure carburization has the benefit of having oxidation-free production and being ecofriendly. However, compared with the low-pressure carburization of the low-alloy steel, low-pressure carburization of the 14Cr14Co13Mo4 steel consumes more time and has a risk of network carbides. In order to promote carbon diffusion and avoid network carbide, Fe–Ni films with various thickness were electrodeposited on the 14Cr14Co13Mo4 steel prior to low-pressure carburization. The experimental results show that, under the same carburizing conditions, the surface carbon content decreases and the carburized layer increases with the increase of Fe–Ni film thickness. After the hardening heat treatment, the effective case depth (ECD) of the sample coated with 6.0 μm Fe–Ni film was increased by 29% compared to that of the uncoated sample. The morphology of carbides was a strip-shaped, discontinuous network distribution in the uncoated sample, while in the Fe–Ni coated samples, the carbides changed to a globular, uniformly dispersed distribution. The effect of Fe–Ni film on the low-pressure carburizing of steel is explained by the simulation of the carbon diffusion using DICTRA software. The Fe–Ni films reduce the steel surface carbon content in each boost stage of low-pressure carburizing and release carbon atoms in every diffusion stage. Through this adjustment mechanism, the steel surface carbon content can be reduced and carburized layer growth can be promoted.

Improving the thermal stability of nickel thin films on sapphire by a minor alloying addition of gold

Thin metal films deposited on ceramic substrates tend to undergo dewetting (agglomeration) at elevated temperatures even in the solid state. We characterized the dewetting of 40 nm thick Ni films on sapphire in the temperatures range of 700–900 °C and explored the effect of a minor (below 1 at.%) Au doping on the dewetting kinetics. The Ni film was doped with Au in three different ways: by a uniform alloying, by depositing a Ni-Au-Ni trilayer, and by depositing a Au overlayer on the Ni film. We found that Au additions decrease the dewetting rate of Ni films and increase their stability at high temperatures. We discuss this phenomenon in terms of increase of surface anisotropy of Ni caused by surface segregation of Au. The increased anisotropy reduces the extent of thermal grooving at the grain boundaries and retards the formation of dewetting holes. The strongest retardation of dewetting was observed in Ni films with Au overlayer. We discuss this observation in terms of the dominance of the surface diffusion path in the dewetting process.

GaN nanostructures by reactive ion etching: Mask and Maskless approach

GaN nanostructures have been fabricated by reactive ion etching (RIE) with and without mask. The mask comprising of self assembled nanoparticles has been prepared by rapid thermal annealing (RTA) of thin film of Ni deposited on GaN epilayers grown by Metal Organic Vapor Phase Epitaxy (MOVPE). Effect of RTA temperature and time on the morphology of mask has been studied using 5 and 10 nm thick Ni films. Using 5 nm Ni film, a good mask composed of sub 50 nm agglomerated nanoparticles in high density (>1E10 /cm2) was fabricated at 850 °C after 90–120 s of RTA. The samples were subjected to BCl3/Cl2 plasma based inductively coupled plasma RIE (ICP-RIE) process to fabricate the nanostructures. The morphology of the fabricated nanostructures exhibited direct correspondence to the Ni mask used. No etching was observed in material underneath the mask area. Conical nanostructures were fabricated in high density with diameter and height of 100 nm and 150 nm. The size of the nanoparticles was identified as the major limitation to fabricate high aspect one dimensional structures like nanowires using this approach. To overcome this limitation, a novel maskless RIE process has been employed with careful choice of process parameters and nanowires with sub 40 nm diameter and 280–300 nm height were successfully fabricated in high density (∼1E10 /cm2) using GaN epilayers with high dislocation density.

Коррекция характеристик обратного восстановления высоковольтных инжекционных 4H-SiC диодов с помощью протонного облучения

The effect of proton irradiation on electrical characteristics of high-voltage (3 kV) 4H-SiC junction diodes have been investigated. The diodes were irradiated through 10-µm thick Ni-film. The energy of protons and irradiation dose were 2.8 MeV and 4×1011 cm-2, respectively. After proton irradiation, the diodes exhibited 35-% increasing in on-state resistance, about 3 times decreasing in the reverse recovery charge with the reverse recovery character being "hard".

Growth and orientation relationships of Ni and Cu films annealed on slightly miscut [formula omitted] r-sapphire substrates

Nano-crystalline Ni and Cu films deposited on the r-plane of sapphire (α-Al2O3) develop a 〈1 1 1〉 fiber-texture upon annealing, in which grains grow up to 300 to 500 times larger than the film thickness. Most of the largest grains, which have grown at the expense of others, display one of four preferred orientation relationships (ORs) to the substrate. The four preferred ORs are OR1r = Me(1 1 1)[11¯0]//α-Al2O3(11¯02)[112¯0], OR2r = Me(1 1 1)[11¯0]//α-Al2O3(11¯02)[1¯101] (Me = Ni or Cu), and their twins, which are rotated 60° about the 〈1 1 1〉 axis perpendicular to the substrate. For these ORs, one of the densest 〈1 1 0〉 atomic rows that lies within the Me {1 1 1} interfacial plane, aligns with the direction of the step edges that form at the intersection of the r-plane with one of its neighboring facets on the equilibrium shape of sapphire (i.e. the c- (0 0 0 1), p-{112¯3} or s{101¯1}-planes). One of the ORs is most preferred when the steps at the interface are such that a {1 0 0}-type ledge of the Me {1 1 1} interfacial plane faces the ledge of the sapphire step. This observation provides a useful insight into the origin of the preferred ORs, and confirms the important role of surface steps in texture development. The evolution of Ni films of different thicknesses, ranging from 100 to 560 nm, was analyzed. Grain boundary grooving inhibits grain boundary motion and favors hole formation and dewetting in the thinnest films (100 nm). The crystals left behind after dewetting display ORs which may differ from the preferred ones. Large grains with the preferred ORs can grow at the expense of others when the film thickness is greater than 300 nm.

Solid-phase diffusion controlled growth of nickel silicide nanowires for supercapacitor electrode

This work reports on the influence of nickel (Ni) thickness on the growth of nickel silicide nanowires (NiSi NWs) using a solid-phase diffusion controlled growth treatment. The NiSi NWs were grown on two different substrates (i.e. crystal silicon (c-Si) and Ni foil) which were coated with Ni film with different thicknesses; 110 ± 5 and 220 ± 5 nm. FESEM images revealed that the shape, the size and the density of NiSi on both substrates were strongly dependent on the thickness of Ni film. These NWs exhibited morphology of straight NWs with diameter and length of between 16 to 23 nm and 2.9 to 3.9 µm, respectively. The NWs showed a single-crystalline Ni3Si2 phase with a preferred orientation in the (1 0 0) plane. XRD diffractogram proved that the formation of Ni-rich NiSi NWs is strongly dependent on the Ni film’s thickness rather than on the types of substrates. NiSi NF220 demonstrated the highest specific capacity with a maximum value of 313.3 C/g. This is attributed from the high density of NWs which endows more redox reaction and the high conductivity of Ni foil substrate that facilitated the high charge transfer kinetics. The fabricated NiSi NWs//activated carbon-based asymmetric supercapacitor exhibited the maximum energy density of 13.37 W h/kg at 200 W/kg and good cyclic stability with 79% capacity retention after 3000 cycles.

The influence of contact material on lateral wet-etching of nickel thin films in lamellae structure

The characteristics of lateral Ni film etching by nitric-acid-based etchant are examined using samples with patterned lamellar layers consisting of SiO2/Ni/Al2O3/Ni/Al2O3 toward the fabrication of hierarchical structures. The lateral etching length increased with increasing etching time, despite the difficult penetration of the etchant through the nanoscale passages in the lamellar layers. However, a higher etching rate (2.1 nm s−1) was observed in the lower Ni film that is in contact with SiO2 and Al2O3 layers on the bottom and top, respectively, compared to that (1.6 nm s−1) of the upper Ni film that contacts with only Al2O3 on both bottom and top sides, due to stronger wetting of SiO2, inducing easier penetration of the etchant into the nanoscale passage between the surrounding layers. Moreover, the influence of Ni film thickness on the lateral etching characteristic was also investigated. The difference in the lateral etching length of the upper and lower Ni films decreases when the Ni film thickness is increased, because of the reduced proportion of the interface region with respect to the Ni-film volume. Despite different contact materials, similar lateral etching lengths were observed in the 150-nm-thick Ni films due to negligible effect of the contact materials in the lamellar structure.

Microstructure, thickness and sheet resistivity of Cu/Ni thin film produced by electroplating technique on the variation of electrolyte temperature

In this research, it has been made Cu/Ni thin film produced with electroplating technique. The deposition process was done in the plating bath using Cu and Ni as cathode and anode respectively. The electrolyte solution was made from the mixture of HBrO3 (7.5g), NiSO4 (100g), NiCl2 (15g), and aquadest (250 ml). Electrolyte temperature was varied from 40°C up to 80°C, to make the Ni ions in the solution easy to move to Cu cathode. The deposition was done during 2 minutes on the potential of 1.5 volt. Many characterizations were done including the thickness of Ni film, microstructure, and sheet resistivity. The results showed that at all samples Ni had attacked on the Cu substrate to form Cu/Ni. The raising of electrolyte temperature affected the increasing of Ni thickness that is the Ni thickness increase with the increasing electrolyte temperature. From the EDS spectrum, it can be informed that samples already contain Ni and Cu elements and NiO and CuO compounds. Addition element and compound are found for sample Cu/Ni resulted from 70° electrolyte temperature of Ni deposition, that are Pt and PtO2. From XRD pattern, there are several phases which have crystal structure i.e. Cu, Ni, and NiO, while CuO and PtO2 have amorphous structure. The sheet resistivity linearly decreases with the increasing electrolyte temperature.

Controlling defects in fine-grained sputtered nickel catalyst for graphene growth

Sputter-prepared nickel (Ni) films can lose more than half their starting thickness due to evaporation in hydrogen (H2) annealing environments. The loss rate of the sputtered Ni films during the chemical vapor deposition growth of graphene has not been reported earlier. The evaporation rate of sputtered Ni film with the amorphous, mixed, preferred ⟨111⟩ texture was experimentally determined to be 20, 11, and 6 nm/m, respectively. An increase of argon mixture in H2 was found to reduce pitting defects in the films during annealing. The quality of grown graphene on top of the Ni improved when the growth temperature was raised from 900 to 1000 °C, as monitored by Raman spectroscopy. More importantly, loss in the starting Ni film thickness can inhibit the growth of graphene layers. By maintaining the growth of the graphene to two layers or less, a high optical transparency of 95% or better can be achieved.

Anomalous Nernst effect of Ni–Al alloys and application to spin Seebeck devices

We have investigated the electromotive force of the spin Seebeck effect and anomalous Nernst effect as a function of Ni film thickness. As Ni film becomes thinner, the electromotive force becomes larger. We also confirmed that the electromotive force of Ni/Ce:YIG samples is higher than that of Pt/Ce:YIG. On the other hand, it is reported that the anomalous Nernst effect of Fe is enhanced by Al addition. However, the effect of Al addition to Ni has not yet been reported. Therefore, we have investigated the anomalous Nernst effect of Ni–Al alloys. As a result, it was found that the appropriate annealing temperature is over 900 °C and the electromotive force is highest with the composition of Ni0.7Al0.3.

Влияние низкодозного протонного облучения на характеристики инжекционных диодов на основе 4H-SiC

AbstractThe effect of low-dose proton irradiation (irradiation dose 10^10–1 . 8 × 10^11 cm^–2) on the capacitance–voltage, forward current–voltage, and reverse-recovery characteristics of 4 H -SiC p – n _ o junction diodes is studied. Irradiation is performed with 1.8-MeV protons through a 10-μm-thick Ni-film (the proton energy and Ni-film thickness were chosen so that the projected proton range in silicon carbide is approximately equal to the p – n _ o junction depth). It is shown that proton irradiation in the above doses (i) does not change the concentration of majority carriers, (ii) leads to a dramatic decrease in the lifetime of nonequilibrium carriers (at a low injection level) (by several tens of times at the highest irradiation dose), and (iii) decreases the reverse-recovery charge at a high injection level (by up to a factor of 3 at the highest irradiation dose).

Preparation of NiPt Alloys by Galvanic Replacement Reaction on Ni Films for Direct Ethanol Fuel Cell

NiPt alloys were prepared successfully by galvanic replacement reaction on the surface of Ni films. The electrolytic deposition of Ni films was investigated to get the high qualities of Ni films for the galvanic reaction. The influence of the electrolytic currents on the morphology and thickness of Ni films were observed by SEM. The thickness and roughness of the Ni films increase with the increase of electrolytic currents. XRD patterns showed that Ni films were formed in the crystal phase of Ni corresponding to face centered cubic structure. Pure Ni films obtained by annealing the films in hydrogen medium were used to prepare NiPt alloys due to galvanic reaction of Pt2+ with Ni2+ in H2PtCl6 solution. The influence of the H2PtCl6 solution concentration on the composition of NiPt alloys were investigated by EDX. The analyses results showed that NiPt alloy formed by using high solution concentration of H2PtCl6 has high composition of Pt. The electrocatalytic activities of both Ni films and NiPt alloys toward ethanol oxidation in KOH medium were carried out by the cyclic voltammetry measurement. Alloyed samples exhibited high electrocatalytic activities due to carbonaceous removal and weakening Pt-COads bond.

Domain structure and magnetization curves of films with perpendicular anisotropy

Based on a two-dimensional micromagnetic simulation, the dependence of the period of a stripe domain structure on the thickness of Co(0001) and Ni(111) films has been obtained, which agrees well with the experimental data. A comparison has been carried out of the calculated and experimental hysteresis loops for a 50-nm Co film and 200-nm Ni film.

Enhanced water splitting performance of GaN photoanode using self-assembled nickel/nickel-oxide nanoparticle catalyst

Ni/NiOx core-shell nanoparticles were used to improve the water splitting efficiency and stability of an n-GaN photoanode. Nanoparticles were fabricated by thermal annealing and oxidizing a Ni thin film deposited on an n-GaN substrate. The performance of water splitting was investigated by varying Ni film thickness and oxidation time, which led to different nanoparticle distribution and NiOx thickness in the core-shell structure. Nanoparticles fabricated from a thinner Ni film led to a smaller particle-to-particle spacing. It allowed holes in n-GaN to diffuse to nanoparticle catalysts in a shorter distance for water splitting reaction, thereby providing higher photocurrent and better protection against oxidation corrosion. Ni/NiOx core-sell nanoparticles obtained from partial oxidation showed higher photocurrent than sole Ni or fully oxidized NiOx nanoparticles. It is attributed to the optimization between having more NiOx for reaction centers and keeping NiOx thin for easy hole transport from n-GaN across NiOx to NiOx/electrolyte interface for reaction.