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In this letter, the growth of dense W2C nanowires by a simple thermal annealing of sputter-deposited WCx films in nitrogen ambient is reported. Straight nanowires with a density of 250–260μm−2 and length∕diameter in the range of 0.2–0.3μm∕13–15nm were obtained from the 700°C-annealed samples, which exhibit good electron field emission characteristics with a typical turn-on field of about 1.7V∕μm. The self-catalytic growth of W2C nanowires is attributed to the formation of α-W2C phase caused by carbon depletion in the WCx films during thermal annealing.

Extrinsic atoms were doped into multiwalled carbon nanotubes (MWCNTs) using microwave plasma-enhanced chemical vapor deposition. Doped nitrogen atoms alter the original parallel graphenes into highly curved ones including some fullerene-like structures. Doped nitrogen atoms could replace carbon atoms in MWCNTs and therefore increase the electronic density that enhances the electron field emission properties. On the other hand, the incorporation of boron into the carbon network apparently increases the concentration of electron holes that become electron traps and eventually impedes the electron field emission properties. Fowler–Nordheim plots show two different slopes in the curve, indicating that the mechanism of field emission is changed from low to high bias voltages. β values could be increased by an amount of 42% under low bias voltages and 60% under high bias voltages in the N-doped MWCNTs, but decreased by an amount of 8% under low bias region and 68% under high bias voltage in the B-doped MWCNTs.

We report on the preparation and field emission properties of quasi-aligned silicon carbon nitride (SiCN) nanorods. The SiCN nanorods are formed by using a two-stage growth method wherein the first stage involves formation of a buffer layer containing high density of nanocrystals by electron cyclotron resonance plasma enhanced chemical vapor deposition and the second stage involves using microwave plasma enhanced chemical vapor deposition for high growth rate along a preferred orientation. It should be noted that growth of the SiCN nanorods is self-mediated without the addition of any metal catalyst. Scanning electron microscopy shows that the SiCN nanorods are six-side-rod-shaped single crystals of about 1–1.5 μm in length and about 20–50 nm in diameter. Energy dispersive x-ray spectrometry shows that the nanorod contains about 26 at. % of Si, 50 at. % of C, and 24 at. % of N. Characteristic current–voltage measurements indicate a low turn-on field of 10 V/μm. Field emission current density in excess of ...

In this letter, we investigate a metalization process for reducing the contact resistance on undoped GaN layers. The Si metal source was diffused successfully into the GaN films by using SiOx/Si/GaN/Al2O3 structures. By using a high-temperature annealing process, we diffused and activated the Si atoms into the GaN film. This caused a heavy doped n-type GaN layer to be formed near the GaN surface. Under high temperatures, such as a diffusion process at 1000 °C, the as-deposited Ni/Al/Ti contact had good ohmic properties and a low specific contact resistivity (ρc) of 1.6×10−3 Ω cm2. Rapid thermal annealing the contact at 800 °C for 30 s caused the ρc to decrease rapidly to 5.6×10−7 Ω cm2. The Ni/Al/Ti contact characteristics on the GaN films diffused at various temperatures are also discussed.

A short H2 plasma treatment of the gate SiNx before depositing amorphous silicon (a-Si:H) is found to significantly decrease the threshold shifts in the bias stress, inverted a-Si:H thin film transistors (TFTs). The reduced threshold voltage shift is attributed to a plasma induced reconstruction of SiNx precursors leading to the removal of the weak bonds. A prolonged plasma treatment, however, degraded the TFT characteristics; this was traced H2 plasma damage which eventually generated a rough a-Si:H/SiNx interface.

Thin‐film transistors (TFTs) with different silicon nitride (SiNx) gate compositions and various hydrogen concentrations in their amorphous silicon films (a‐Si:H) have been stressed with positive and negative biases to realize the instability mechanisms. For both stress polarities, it is found that the threshold voltage shifts significantly increase due to the trap sites in the SiNx gate. As the effects of the trapped charges in the SiNx films are reduced, the anomalous threshold voltage shifts under negative stress voltage are observed. The creation of the states near the conduction band in the a‐Si:H films can be enhanced according to the defect pool concept and stimulated by the hydrogen contents in the a‐Si:H films, which can be confirmed by the subthreshold swing change. Therefore, the negative threshold voltage shifts caused by the hole trapping in the SiNx gate are positively compensated by the created states, reflecting the turnaround behaviors for the threshold voltage shifts. As for the positive...

The hydrogenated amorphous silicon (a‐Si:H) thin film transistors (TFTs) with silicon nitride as a gate insulator have been stressed with negative and positive bias to realize the instability mechanisms. It is found that the threshold voltages of the a‐Si:H TFTs are positively shifted under low negative bias stress and then negatively shifted for large negative gate bias. The positive threshold voltage shift is ascribed to the increased states in the band gap near the conduction band by the negative gate bias. As the negative bias continuously increases, the hole trapping in the silicon nitride or at the a‐Si:H/silicon nitride interface will become dominant, resulting in the negative threshold voltage shift. A similar turnaround phenomenon is also observed with respect to the stress time. On the other hand, for the TFTs stressed with positive gate bias, the monotonic increase of the threshold voltage shift with stress time is attributed to the state creation. Nevertheless, the distributions of the created states in the energy band gap for the a‐SiH TFTs after the stress will be affected by the bias polarity based on the defect pool model, reflecting the asymmetrical subthreshold swing change against the positive and negative stress bias.

β‐SiC (3C–SiC) films were deposited on silicon substrates by electron cyclotron resonance chemical vapor deposition from SiH4/CH4/H2 mixtures at 500 °C. The crystalline structure and chemical composition of the deposited film were found to depend on the SiH4/CH4 flow ratio. With a sufficient energy supply from microwave power and a SiH4/CH4 flow ratio of 0.5 and lower, stoichiometric SiC could be deposited on Si substrates. Microcrystalline β‐SiC was grown at a SiH4/CH4 flow ratio of 0.5, whereas amorphous SiC was obtained at the SiH4/CH4 flow ratios lower than 0.5. When the SiH4/CH4 flow ratio was above 0.5, only polycrystalline Si could be deposited.

Excellent shallow p+n junctions have been formed by implanting BF2+ ions into thin polycrystalline Si films and subsequent annealing; these junctions which show a leakage of 1 nA/cm2 and a junction depth of about 0.05 μm. An anomalous boron diffusion occurs when subsequent silicidation is carried out. Silicidation using 300‐A Ti just slightly affected the junction profile. However, the junction is considerably deepened for 600‐A Ti silicidation, yielding a resulting depth of about 0.11 μm. The large boron redistribution is attributed to the point defects induced by silicidation. Hence, proper silicide thickness should be chosen to retain the junction profile as well as to reduce the parasitic source/drain resistance.

The carbon nanotube network decorated with Pt nanoparticles (PtCNT) irradiated by excimer laser as counter electrode (CE) of dye-sensitized solar cells (DSSCs) has been systematically demonstrated. The conversion efficiency would be improved from 7.12% to 9.28% with respect to conventional Pt-film one. It was attributed to the enhanced catalytic surface from Pt nanoparticles and the improved conductivity due to the adjoining phenomenon of PtCNTs irradiated by laser. Moreover, the laser annealing could also promote the interface contact between CE and conductive glass. Therefore, such a simple laser-irradiated PtCNT network is promising for the future flexible DSSCs applications.

The effects of rapid thermal annealing (RTA) and laser annealing (LA) on the activation and diffusion of ion‐implanted boron in Si substrate have been investigated. The implant and anneal regimes, forming good shallow junctions, were presented. The Si+‐preamorphized samples boron implanted with a high dosage showed largely enhanced diffusion in RTA processing. The LA process serves as an excellent scheme to effectively activate the dopant and suppress the anomalous diffusion because of its very high heating rate. A high‐quality p+/n junction with a leakage current density lower than 2 nA/cm2 and a forward ideality factor of about 1.01 was formed by laser processing.

A TiSi2 silicided shallow n+p junction with a leakage current density of about 3 nA/cm2, a forward ideality factor of 1.00, and a junction depth of about 0.11 μm has been fabricated by implanting P+ ions into thin amorphous‐Si/Ti bilayer films on silicon substrate and subsequently processed by a rapid thermal annealing (RTA) at 800 °C/60 s with a post‐conventional furnace annealing (CFA) at 600 °C/30 m. RTA not only minimizes the diffusion of knock‐on Ti into the junction region, but also facilitates the silicidation and damage annihilation. The low‐temperature CFA treatment following the high‐temperature RTA process greatly increases the diffusion of dopants into the junction region and thus improves the junction characteristics significantly. The increased diffusion of dopants from the silicide layer into the junction region by the post‐CFA process is attributed to the crystallization of the titanium silicide.

Programmable metallization cell (PMC) memory devices with oxidized Cu-Ti alloy films as the bottom electrodes have been shown to exhibit a superior on/off state current ratio (memory window) of as high as 103 and endurance of 3000 cycles as compared to conventional pure copper and unoxidized Cu-Ti alloy electrodes. It was conjectured that the Cu-Ti alloy electrodes could obtain the appropriate amount of copper atoms to format and rupture the conductive filaments in the resistive switching layer. Furthermore, the oxidized Cu-Ti alloys could control the Cu cations from the Cu and Cu2O to the appropriate amountto achieve the most favorable PMC characteristics.

In this paper, the surface morphology transformation of the sprayed carbon nanotube (CNT) thin film irradiated with the excimer laser has been systematically investigated. Under the excimer-laser irradiation, two phenomena, including the annealing and ablation effects, were found to be dependent on the incident laser energy and overlapping ratios. Moreover, the extremely high protrusions would be produced in the interface between the annealing and ablation regions. The mechanism of the CNT thin film under the excimer laser irradiation was, therefore, proposed to derive the surface morphology modifications and the further reinforced crystallinity with proper laser energy densities and overlapping ratios.

An excimer-laser-crystallized polycrystalline-silicon silicon-oxide-nitride-oxide-silicon thin-film transistor with recessed-channel structure has been designed to achieve only one grain boundary with a protrusion perpendicular to the channel for investigating the grain boundary location effects on the memory characteristics. After programming, the devices demonstrated better memory characteristics as the grain boundary was allocated near the source junction. In contrast, the memory characteristics were degraded when the grain boundary was located near the drain junction. The phenomenon was explained by the 2-D device simulation and the energy band diagrams.

The recovery mechanism of the light-induced instability of amorphous InGaZnO thin-film transistors was examined. Following light illumination, the bare devices displayed more dark recovery of the threshold voltage (Vth) shifts than the ones encapsulated in nitrogen ambient. This was attributed to the adsorption of more oxygen (O2) in the back channel of the bare devices. Further, much more recovery was also observed for the bare devices than the nitrogen-encapsulated ones under positive gate bias. This implied the recovery effect under gate bias could be further enhanced because the induced electrons could greatly increase the adsorption of more O2 for the bare devices.

The nitrogen ambient encapsulation (NAE) technique is introduced to improve the reliability issue for the amorphous InGaZnO (a-IGZO) thin-film transistors under positive gate bias stress (PGBS). For the NAE devices, the threshold voltage (Vth) shift is significantly decreased from 1.88 to 0.09 V and the reduction of saturation drain current is improved from 15.75 to 5.61 μA as compared to the bare a-IGZO counterparts after PGBS. These improvements are attributed to the suppression of negatively charged oxygen adsorption on the a-IGZO backsurface and thereby well maintain the channel potential of NAE devices, which in turn sustain the Vth during PGBS.

In this letter, gate-all-around (GAA) polycrystalline silicon thin-film transistors (TFTs) with self-aligned grain-growth channels were fabricated using excimer laser crystallization (ELC) on a recessed-nanowire (RN) structure. Via the RN structure constructed by a simple sidewall-spacer formation, location-controlled nucleation and volume-confined lateral grain growth within the RN body during ELC process have been demonstrated with only one perpendicular grain boundary in each nanowire channel. Because of the high-crystallinity channel together with GAA operation mode, the proposed GAA-RN TFTs show good device integrity of lower threshold voltage, steeper subthreshold slope, and higher field-effect mobility as compared with the conventional planar counterparts.

In this paper, location-controlled silicon crystal grains are fabricated by the excimer laser crystallization method which employs amorphous silicon spacer structure and prepatterned thin films. The amorphous silicon spacer in nanometer-sized width formed using spacer technology is served as seed crystal to artificially control superlateral growth phenomenon during excimer laser irradiation. An array of 1.8-μm-sized disklike silicon grains is formed, and the n-channel thin-film transistors whose channels located inside the artificially-controlled crystal grains exhibit higher performance of field-effect-mobility reaching 308cm2∕Vs as compared with the conventional ones. This position-manipulated silicon grains are essential to high-performance and good uniformity devices.

Single‐crystal CoSi2 films have been grown in solid phase epitaxy regime under nonultrahigh vacuum conditions on (111) Si by electron gun deposition of Co thin films followed by rapid thermal annealing in Ar ambient. The single‐crystal films were analyzed by transmission electron microscopy to share the (111) Si surface normal but are rotated 180° about that axis with respect to the substrate. The effect of gas ambient was found to be of critical importance in the growth of single‐crystal CoSi2 on (111) Si. The present nonultrahigh vacuum treatments to grow single‐crystal films on silicon shall greatly facilitate the fabrication of novel classes of high‐speed and high‐frequency devices employing buried silicide layers.

Thin interposing Ni layers between Fe thin films and substrate Si have been shown to be very effective in inducing the growth and improving the quality of epitaxial FeSi2 on silicon. The formation of a transition layer with graded concentration is conceived to facilitate the epitaxial growth of FeSi2 on silicon. The thin interposing layer scheme may be extended to promote the epitaxial growth of a number of refractory silicides on silicon.