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(Bi1−x Sb x )2S3 solid solution nanowires ( 0 ≤ x ≤ 0.73 ) are grown on fluorine-doped tin oxide (FTO) glass via physical vapor transport. The compositions were controlled by varying the Sb2S3 source temperature (300 °C–453 °C) by changing the upstream locations of the Sb2S3 source in the furnace while keeping the Bi2S3 source at the center of the furnace (497 °C). Defect-free nanowires with phase-pure orthorhombic and quasi-1 dimensional crystal structures were grown under a modified vapor–solid mechanism affected by FTO at initial growth stage. The aspect ratios of the nanowires reached the minimum at composition x ∼ 0.6 . As the Sb2S3 source approached the Bi2S3 source, x increased owing to the increase in the Sb2S3 source temperature. x/(1-x), which is proportional to the evaporation flux of the Sb2S3 source, could be well-fitted with a thermally activated equation with an apparent activation energy ( 105 kJ mol - 1 ). However, at the distance between the Sb2S3 and Bi2S3 sources, with the Sb2S3 source at temperatures higher than 410 °C, the compositions reduced despite the increased Sb2S3 evaporation flux. Such retrograde behavior was confirmed by high-resolution transmission electron microscopy, x-ray diffraction, and micro-Raman studies. This retrograde behavior is ascribed to the loss due to the reaction of gaseous Sb species with the Bi2S3 source.

Advances in modern electronic technologies have been driven toward combining the continued miniaturization of device components and their deterministic integration onto unconventional platforms. This effort aims at achieving electronic devices of various form factors with exotic functionalities, which has been foreseen to be impossible with any traditional approaches. Amongst a variety of "futuristic" technologies, mechanically reconfigurable devices which can be reversibly stretched, twisted, and folded under severe mechanical deformation and harsh operational conditions offer an enormous amount of unprecedented opportunities. Traditional device manufacturing schemes have relied on three-dimensional silicon (Si)-based wafers, which are intrinsically bulky and rigid, requiring highly complicated and unstainable fabrication steps for the inclusion of such mechanical deformability. This fundamental challenge invokes innovations in materials design and processing, triggering to explore a new type of electronic materials that can intrinsically possess superior materials properties even at extremely small length-scales. Recently discovered two-dimensional (2D) transition metal dichalcogenides (TMDs) offer a rich set of unparalleled properties in a wide range of optical, electrical, and mechanical aspects unattainable with Si. Moreover, they offer uniquely suited advantages for mechanically reconfigurable electronics owing to their extremely large mechanical tolerance and small thickness coupled with van der Waals (vdW) attraction-enabled relaxed assembly requirement. In this review, we report an extensive overview of up-to-date progress in exploring 2D TMD layers for mechanically reconfigurable electronic devices, particularly focusing on large-area devices by noting their technological and practical relevance. We systematically overview the material property suitability of 2D TMD layers for reconfigurable electronics and their fabrication and integration strategies as well as proof-of-concept demonstrations available in the literature. We also discuss current technical challenges associated with developing high-performance 2D TMDs-based devices and offer forward-looking perspectives for this emerging technology.

Elastic metasurfaces are artificial thin layers composed of sub-wavelength structures designed to manipulate wave propagation such as anomalous refraction/reflection. Despite recent active researches, achieving a really thin metasurface has been a challenge, since it has been almost impossible to design a single unit to satisfy both the 2π phase span and the full transmission. In this paper, we revealed the way to achieve both conditions by a single unit so that a really thin elastic metasurface is possible. Here, we found that the single unit should have not only positive, but negative effective parameters to achieve both the 2π phase span and the full transmission. To realize such a single unit, we design resonance-based metasurface units consisting of two types of resonators: vertical and horizontal resonators, which individually modulate effective stiffness and mass, respectively. By adjusting each resonator, any desired effective parameters from negative to positive values can be tuned, achieving both the 2π phase span and the full transmission. Numerical validations are carried out for the proposed metasurface unit. Finally, various single-unit elastic metasurfaces are designed with the proposed metasurface unit for anomalous refraction. Since extremely thin elastic metasurface consisting of a single unit is possible, we expect our research to be able to open a new field in wave tailoring applications.

The Bragg gap that stops wave propagation may not be formed from zero or a very low frequency unless the periodicity of a periodic system is unrealistically large. Accordingly, the Bragg gap has been considered to be inappropriate for low frequency applications despite its broad bandwidth. Here, we report a new mechanism that allows formation of the Bragg gap starting from a nearly zero frequency. The mechanism is based on the finding that if additional spin motion is coupled with the longitudinal motion of a mass of a diatomic mechanical periodic system, the Bragg gap starting from a nearly zero frequency can be formed. The theoretical analysis shows that the effective mass and stiffness at the band gap frequencies are all positive, confirming that the formed stop band is a Bragg gap. The periodic system is realized by a spin-harnessed metamaterial which incorporates unique linkage mechanisms. The numerical and experimental validation confirmed the formation of the low-frequency Bragg gap. The zero-frequency Bragg gap is expected to open a new way to control hard-to-shield low-frequency vibration and noise.

Transmit–receive devices (TRD) monolithically integrated with a butt-coupled semiconductor optical amplifier (SOA) have been designed and fabricated using a buried ridge/ridge waveguide structure with low-threshold-current and high-temperature operation characteristics. The maximum output power was 31 mW under CW operation at 25 °C. At 85 °C the output power was over 9 mW with a side mode suppression of over 45 dB. The responsivity of the detector photodiode was over 0.6 A/W in the temperature range between 25 and 65 °C and over 0.3 A/W at 85 °C. It was nearly constant in the input-power range between -30 to -10 dBm.

We propose two types of novel scheme for reducing the number of output channels of driver-integrated circuit (D-IC) for the current programming compensation pixel structures of active-matrix organic light-emitting diodes (AMOLEDs). One is a 2:1 data demultiplexing technique that can reduce the number of output channels of D-IC by half. The proposed second scheme is a vertically aligned red (R), green (G), and blue (B) subpixel scheme instead of a horizontally aligned R–G–B subpixel one, which is regarded as the conventional pixel alignment scheme. We have also successfully implemented these schemes in a 2.4-in.-sized QCIF + (176 × RGB × 220) AMOLED using p-type excimer laser annealing (ELA) low-temperature polycrystalline silicon (LTPS) technology and evaluated key performance characteristics.

We grew In nanowires on In-rich InGaN layers with In content of 80% using focused ion beam system equipped with Ga liquid metal source. The experiments were performed at room temperature without any cooling or heating source, and the whole growth process can be monitored in-situby field emission scanning electron microscope / FIB dual beam system. The nanowires were observed only at the ion beam irradiation area, and the length and diameter of nanowires were controlled by adjusting accelerating voltage. The energy dispersive x-ray spectroscopy and the electron diffraction pattern of nanowires using transmission electron microscope confirmed that the composition of nanowire was indium, and the In nanowire was grown along the [-1 1 2] direction. This In nanowire induced by FIB irradiation grew with the ultra-fast growth rate as fast as 8 μ/min. The growth of In nanowires was supposed to be caused by ion irradiation-induced phase decomposition.

A hybrid passivation method a using parylene and silicon dioxide combination layer for a film-like organic light-emitting diode (OLED) was applied on a polycarbonate substrate. Parylene coating by vapor polymerization is a highly effective passivation process for the OLED, and it is applied to the entire top surface and the edges of the OLED device. To minimize the permeation of moisture and oxygen from the top surface of the device, an additional layer of silicon dioxide was deposited over the parylene-coated layer. It was found that the water vapor transmittance rate (WVTR) of parylene (15 µm in thickness)/SiO2 (0.3 µm in thickness) combination layers deposited on the polycarbonate film was decreased to less than 10-3 g/(m2d). The OLED that had undergone hybrid passivation showed significantly longer lifetime characteristics in ambient conditions than the non-passivated OLED. The lifetime of the passivated OLED was 400 h and it was more than ten times the lifetime of the conventional non-passivated OLED.

We present an evaluation of the frequency shifts in an optically pumped caesium-beam frequency standard caused by the neighbouring transitions. We analyse the shifts caused by the Rabi and Ramsey pulling effects and find a well-known result for the Rabi pulling but a new result for the Ramsey pulling. The revised Ramsey shift is found to be proportional to not the imaginary but the real part of the ground-state atomic coherence. The value of the Ramsey shift is proportional to the first power of the Rabi frequency defined by a small orthogonal component of the microwave field and the inverse value of the Zeeman splitting. We compare the shifts caused by the neighbouring transitions and show that the relative contributions of the Rabi and Ramsey pulling effects crucially depend on the quality of optical pumping. We estimate that the Rabi shift for the KRISS-1 caesium-beam frequency standard is at a relative level of 10−14 while the Ramsey shift is at a relative level of 10−12.

The evaluation of skin surface contours can be carried out by various techniques, including the use of a stylus profilometer, a laserprofilometer and a conventional optical profilometer (COP). But these methods have some drawbacks because their data are basically obtained from two-dimensional algorithms. So a new technique has been developed based on a new concept: a stereo image processing technique which is considered in this paper. Since a pair of stereo images contains depth information, the 'disparity', or the difference between the left and right images, enables the production of three-dimensional coordinates. This study was performed to evaluate the change of skin surface contours according to the ageing process. The stereo image optical topometer (SOT) is a new instrument used for the three-dimensional evaluation of skin surface contours. Thus. five new parameters have to be developed, such as mean surface roughness (S(a)), mean depth of roughness (S(z)), three-dimensional length (S(L)), three-dimensional area (S(A)), and three-dimensional volume (S(V)). S(a), S(L) and S(A) have shown a statistically significant increase in the seventies age group. S(z) has also shown a significant increase in the twenties and over-sixties age groups. The coefficient variation of the height of the skin surface using a COP varies between 14.76 and 6.57, but that using a SOT is between 2.18 and 2.69, according to age variation. In conclusion, the SOT system is a more reliable and useful method for evaluating skin surface contours than the COP system. Among the three-dimensional parameters which were made in this study, S(A), S(L) and S(a) seem to be useful as reliable parameters for evaluating skin surface contours in the ageing process.

A micro heat flux sensor which can measure the thermal energy transfer per unit area has been designed, fabricated, and calibrated in a convective environment. The sensor which is based on a circular foil gage is composed of thermal paths and a thermopile. The thermal path is made in a LIGA-like process of SU-8 high aspect ratio microstructures and electroplated copper layers. The thermopile, a series of thermocouples, is used to amplify the output signal as a thermometer. When the sensor is placed on a high-temperature wall, heat flux from the wall flows through thermal paths and drains out to the environment, producing a temperature difference along its paths. Heat flux is obtained by calibrating this temperature difference in the thermopile of Ni-Cr or Al-Chromel pairs. The sensitivity of the heat flux sensor of Ni-Cr and Al-Chromel pairs is in the range of 0.1-2.0 and 0.4-2.0 µV mW-1 cm-2, respectively, in the heat flux range of 0-180 mW cm-2.

This paper presents a study of the anodic bonding technique using a hydrophilic surface. Our method differs from conventional processes in the pre-treatment of the wafer. Hydrophilic surfaces were achieved from dipping in H2O/H2O2/NH4OH solution. The hydrophilic surface has a large number of -OH groups, which can form hydrogen bonds when two wafers are in contact. This induces a higher electrostatic force, because of the decreasing gap between the glass and silicon wafer. We achieved improved properties, such as a wider bonded area and a higher bond strength than those of conventional methods. Also, the fabricated pressure sensors on the 5-inch silicon wafer were bonded to Pyrex #7740 glass of 3 mm thickness. In order to investigate the migration of the sodium ions, the depth profile at the glass surface by secondary-ion mass spectroscopy and the bonding current were compared with that of conventional methods.

An optically pumped caesium-beam frequency standard (known as the KRISS-1) has been constructed at the Korea Research Institute of Standards and Science (KRISS) and the first measurements of long-term frequency stability have been made. Two methods were used to make the frequency standard immune to variations in the environmental temperature: an F = 4 → F' = 3 (σ + π)-polarized laser was used as a pumping source, and the difference between two sequential error signals was used as a feedback signal in the digital servo loop. A frequency stability of σy(τ) = 2.5 × 10-14 at τ = 105 s for a temperature variation of 4 °C was achieved with the KRISS-1.

We performed a silicon-to-silicon anodic bonding process using a glass layer deposited by electron beam evaporation. Corning No 7740 Pyrex glass was used as the source material of electron evaporation. The effects on the bonding process were investigated as a function of the thickness of the glass layer and the concentration of sodium ions in the glass layer. The surface roughness of the glass layer decreased with increasing thickness of the glass layer. It was observed that the deposited glass layers of more than thickness had very small surface roughness. The depth profile of sodium ions showed that the glass layer deposited by electron beam evaporation contained many more sodium ions than the glass layer deposited by sputtering. The silicon-to-silicon bonding process was performed at temperatures in the range of 135 - C with an electrostatic voltage in the range of 35 - . A pull test revealed that the tensile strength of bonded specimens was in the region of 1 - 8 MPa. The role of sodium ions in anodic bonding was studied by investigating the theoretical bonding mechanism and examining the results of secondary-ion mass spectroscopy (SIMS) analysis on the glass layer before and after the bonding process.

We have demonstrated a high-power widely tunable sampled grating (SG) DBR laser integrated monolithically with optical semiconductor amplifier (SOA), using planar buried heterostructure (PBH). The measured threshold current was 5 mA on average with 60 chips randomly selected which is lowest among the typical average values. Fiber-coupled output power was 12.4 dBm and the output power variation was ?1 dB for the whole tuning range.

NASA Kennedy Space Center (KSC) researchers have been working on enhanced and modernized cryogenic liquid propellant handling techniques to reduce life cycle costs of propellant management system for the unique KSC application. The KSC Ground Operation Demonstration Unit (GODU) for liquid hydrogen (LH2) plans to demonstrate integrated refrigeration, zero-loss flexible term storage of LH2, and densified hydrogen handling techniques. The Florida Solar Energy Center (FSEC) has partnered with the KSC researchers to develop thermal performance prediction model of the GODU for LH2. The model includes integrated refrigeration cooling performance, thermal losses in the tank and distribution lines, transient system characteristics during chilling and loading, and long term steady-state propellant storage. This paper will discuss recent experimental data of the GODU for LH2 system and modeling results.

We report a 1.5 μm and 10 Gb s−1 etched mesa buried heterostructure λ/4-shifted distributed feedback laser diode (DFB-LD) for the low-cost application of WDM–based datacenter networks. To reduce the threshold current and improve the modulation bandwidth in a conventional p-/n-/p-InP current blocking structure, a thin undoped-InP (u-InP) layer was inserted between the side walls of the active region and the p-InP layer (i.e., a u-/p-/n-/p-InP structure), and the region containing the active region and the current blocking structures was etched in a mesa form (i.e., an etched mesa). From this work, it was found that a 300 μm long anti-reflection (AR)-AR DFB-LD with a mesa width of 8 μm is reduced by about 25% while a side mode suppression ratio is >50 dB and a 3 dB bandwidth is >10 GHz at a current of 40 mA; in addition, it shows a clear eye-opening with a dynamic extinction ratio of >4.5 dB at 10 Gb s−1, and a power penalty of

Surface functionalized monodispersed Fe3O4 magnetic nanoparticles were synthesized by the polyol method. Surfactants were used to control size, shape and agglomeration of the magnetic nanoparticles during the preparation. The size of these nanoparticles was in the range of 10–30 nm as observed in transmission electron microscopy (TEM). The formation of monodispersed shapes was controlled by varying the surfactants without changing the reaction conditions. The x-ray diffraction (XRD) pattern validates the phase purity and cubic structure even after the addition of surfactants. The functional groups were observed from Fourier transform infrared (FTIR) spectroscopy analysis, confirming the surface modification with polymer molecules in the polyol medium. The saturation magnetization value decreases from 89 to 59 emu g−1 for the surfactant coated Fe3O4 nanoparticles and it also shows superparamagnetic behavior at room temperature. Cell viability rate and percentage of dead cells were accurately identified in human breast carcinoma cell lines using in vitro cell viability experiments, which confirms that pristine and surfactant coated Fe3O4 nanoparticles are non-toxic and can be used for biomedical applications.

Transducers made of thin magnetostrictive patches and magnetic circuits have been recently developed as an effective means for non-destructive guided wave inspection of elastic structures. However, important characteristics of transducers, such as their wave radiation patterns, have been tested only by experiments or a first-order theoretical analysis. There have been some finite element analyses related to magnetostrictive actuators, but no numerical analysis has been performed to predict the wave radiation patterns of various magnetostrictive patch transducers. In this paper, we formulate a finite element procedure and implement it to predict the wave radiation pattern of a magnetostrictive patch transducer installed on a plate. In particular, a linearized model determining coupling matrix appearing in the magnetostrictive constitutive equation of a magnetostrictive patch in a transducer is developed. The developed model is then used to deal with the arbitrarily polarized static magnetic field induced in the transducers. For numerical efficiency, time-harmonic analysis is carried out and a technique to extract data corresponding to target guided wave modes is used. The validity of the developed finite element analysis is checked by comparing the simulated wave radiation patterns from the present analysis with experimental results. The reasons why certain radiation patterns are obtained for selected magnetic circuits are explained by physical reasoning and simulation results.

We have studied the off-bias stress effect on the performance of bottom-gate polycrystalline silicon (poly-Si) thin-film transistor (TFT). The poly-Si was crystallized by metal-induced crystallization through a cap layer (MICC) of a-Si. The poly-Si TFT with a n+ a-Si:H source/drain contacts exhibited a field-effect mobility of 12.4 cm2 V-1 s-1, a gate swing of 0.86 V/dec. and the minimum off-state current of

Angled nano-scale tunnels with high aspect ratio were fabricated on poly(methyl methacrylate) (PMMA) using a focused ion beam (FIB). The fabrication parameters such as ion fluence, incidence angle, and acceleration voltage of the Ga(+) ion beam were first studied on the PMMA surface to explore the formation of the nano-scale configurations such as nano-holes and cones with diameter in the range of 50-150 nm at an ion beam acceleration voltage of 5-20 kV. It was also found that the PMMA surface exposed to FIB was changed into an amorphous graphitic structure. Angled nano-scale tunnels were fabricated with high aspect ratio of 700-1500 nm in depth and 60 nm in mean diameter at an ion beam acceleration voltage of 5 kV and under a specific ion beam current. The angle of the nano-tunnels was found to follow the incident angle of the ion beam tilted from 0 degrees to 85 degrees , which has the potential for creating a mold for anisotropic adhesives by mimicking the hairs on a gecko's feet.

We show that focused ion beam irradiation results in the creation of peculiar one- and two-dimensional nanoscale features on the surface of polyimide-a common polymer in electronics, large scale structures, and the automobile industry, as well as in biomedical applications. The role of ion beam incident angle, acceleration voltage, and fluence on the morphology of the structural features is systematically investigated, and insights into the mechanisms of formation of these nanoscale features are provided. Moreover, by using the maskless patterning method of the focused ion beam system, we have developed a robust technique for controlled modification of the polymeric surface. The technique, which is analogous to using a gray glass with varying darkness to control the radiation from the sun, but at a much smaller scale, enables the ion intensity and angle to be controlled at each surface point of the polymer, giving rise to structural surface features with desired shape and morphology.

According to the experimental investigations, it is reported that the magnetic switching field is varied by the stacking orders in the recording media composed of stacked structure. The lattice distortion due to the lattice mismatch between two layers has been suggested as an origin of the difference; however, it has not been clearly explained up to now. In this paper we studied the possibility of the contribution of the convex surfaces in recording media. The convex surfaces vary the ratio between local magnetic anisotropy and intergranular exchange coupling strength that influences the magnetic behaviours of the stacked granular structure. An analytic model including the local geometric inequivalency is presented. From the analytic equations, it is found that the uniaxial anisotropy of the concave bottom layer can be overcome more easily than other parts, with the assistance of the intergranular exchange. Consequently, the harder bottom layer can be reversed earlier than the softer top layer, under some appropriate conditions. The analytic results are proved by finite element micromagnetic simulations.

A phase change memory (PCM) utilizes resistivity changes accompanying fast transitions from an amorphous to a crystalline phase (SET) and vice versa (RESET). An investigation was made on the SET characteristics of PCM cells with Ge-doped SbTe (Ge‐ST) materials of two different Sb:Te ratios (4.53 and 2.08). For the material of higher Sb:Te (4.53), a SET operation was completed within several tens of nanoseconds via nucleation-free crystallization whereas the material of lower Sb:Te (2.08) rendered a slower SET operation requiring several hundred nanoseconds for a nucleation-mediated crystallization. From measurements of nucleation and growth kinetics via laser-induced crystallization, the observed SET characteristics of the former case were found to derive from a growth time about 10 3 times shorter than the nucleation time and those of the latter from a much shorter nucleation time as well as a longer growth time than in the former case. The measured nucleation kinetics of the lower Sb:Te (2.08) material is unexpected from the existing data, which has led us to advance an interesting finding that there occurs a trend-reversing change in the nucleation kinetics of the Ge-ST materials around the eutectic composition (Sb:Te ∼2.6); nucleation is accelerated with the increase in the Sb:Te ratio above Sb:Te of 2.6, but with a decrease in the Sb:Te ratio below it.

We report on the growth and characterization of patterned and uniformly distributed GaN microcrystals with well-defined facets and epitaxy. The microcrystals were grown on a mask patterned by lithography. The GaN microcrystals were formed by selective-area epitaxy using metal-organic chemical-vapour deposition. The GaN microcrystals have similar sizes and shapes. Each microcrystal consists of an upper and a lower part, which are rotated by 30°. Transmission electron microscopy shows that there is a rather clear interface between the two parts of the crystal, suggesting a sudden change in the growth direction. We performed ab initio calculations for the surface energies of hexagonal GaN, and the growth morphology is explained based on surface energy considerations.

Fully depleted silicon-on-insulator (FD SOI) devices with 70 nm gate lengths for embedded static random access memory (SRAM) technology were investigated for different SOI film thickness. Transistor performances of 700 µA/µm and 320 µA/µm were obtained for n-type and p-type metal-oxide semiconductor field effect transistor (NMOSFET and PMOSFET) devices, respectively at 1.0 V operation voltage and I off=75 nA/µm. Si selective epitaxial growth (SEG) process was well optimized. Both the single raised (SR) and double raised (DR) source/drain process were studied to reduce parasitic series resistance. For the DR process, both NMOSFET and PMOSFET performance are improved by 9 and 13% respectively, compared to the SR process. Drain induced barrier lowering (DIBL) was improved from 100 mV to 13 mV as the SOI film thickness was scaled down from 50 nm to 17 nm. Due to the self-heating effect, the AC current is 15% higher than the DC current for the case of 40 nm SOI thickness. The static noise margin (SNM) for a 1.1 µm2 6T-SRAM cell was 210 mV and ring oscillator speed was improved by 24% compared to bulk devices.

We performed glass-to-silicon bonding and fabricated a hermetically sealed silicon wafer using silicon direct bonding followed by anodic bonding (SDAB). The hydrophilized glass and silicon wafers in solution were dried and initially bonded in atmosphere as in the silicon direct bonding (SDB) process, but annealing at high temperature was not performed. Anodic bonding was subsequently carried out for the initially bonded specimens. Then the wafer pairs bonded by the SDAB method were different from those bonded by the anodic bonding process only. The effects of the bonding process on the bonded area and tensile strength were investigated as functions of bonding temperature and voltage. Using scanning electron microscopy (SEM), the cross-sectional view of the bonded interface region was observed. In order to investigate the migration of the sodium ions in the bonding process, the concentration of the bonded glass was compared with that of standard glass. The specimen bonded using the SDAB process had higher efficiency than that using the anodic bonding process only.

The diffusion behavior of a carbon-acceptor impurity in a p+-n+ GaAs tunnel junction with a heavily carbon doped p+-layer was investigated in detail. The diffusion coefficients of carbon were deduced from the degradation rates of the peak current density of the GaAs tunnel diodes. The current-induced diffusion coefficient of carbon under forward bias operations at 2 kA/cm2 was given by D C,current\sevsize-induced=D 0exp (-E a/k T), where D 0=1.5×10-13 cm2/ s and E a=0.47±0.01 eV. In addition, the thermal diffusion coefficient was given by D C,thermal=D 0exp (-E a/k T), where D 0=1.1×10-9 cm2/ s and the activation energy E a=1.47±0.01 eV.

The relation between film quality and deposition rate of hydrogenated amorphous silicon films deposited by electron cyclotron resonance plasma chemical vapor deposition using H2/SiH4 has been investigated. The properties of amorphous silicon films were improved with increasing deposition rate; photoconductivity increased and optical band gap, full width at half maximum and the ratio of the concentration of dihydride to that of monohydride decreased. The high deposition rate was a very important factor to obtain high quality amorphous silicon films grown by electron cyclotron resonance plasma chemical vapor deposition using H2/SiH4.

The effect of wet-etching process on the gate insulator for fabrication of field emitter arrays (FEAs) was examined. Three types of wet-etching process have been performed to fabricate metal tip FEAs, they are Mo (gate metal), oxide (gate insulator) and Al (release layer) etching, respectively. We examined the effect of gate insulator after wet etching through breakdown field strength and rms surface roughness. And the effect by residual ions or atoms was also examined. The breakdown field strength of gate insulator by the measurement of current-voltage for immersing in oxide etchant was rapidly lowered at the expense of large etching time. However in case of Al etchant, the breakdown field strength was lowered slowly. In all cases, it has been validated through Auger electron spectroscopy (AES) analysis that the residual atom was phosphor after wet-etching process when compared cleaned with non-cleaned samples. Also, we obtained excellent result when aluminum etchant was substituted for 3% tetra-methyl ammonium hydroxide (TMAH). In case of TMAH, decrease of the breakdown field strength was the slowest, surface roughness was smoother, and it did not attack gate and tip material.

We fabricated diamond-like carbon (DLC) coated knife edge-shaped field emitter array (KEFEA) on the (110) silicon wafer. The fabricated KEFEA has more than six hundreds times of aspect ratio and about two times higher electric field at tip-apex compared with the pyramid-shaped edge field emitter array (FEA). A high quality DLC film which has similar properties to the diamond film was coated on the silicon KEFEA by PECVD method in order to improve the stability and electrical characteristics. The turn-on field was lowered from 0.18 MV/cm to 0.14 MV/cm by the DLC film coating to the pure silicon KEFEA. More than 400% of the short-term emitted current fluctuation was observed from the measurement of the pure silicon KEFEA. The DLC film coating on the pure silicon KEFEA reduced the emission current fluctuation to 15%.

Uniform and reproducible silicon tip arrays were fabricated using the reactive ion etching followed by the re-oxidation sharpening. Molybdenum was coated on the some of the silicon tip array. Current-voltage characteristics and current fluctuations were tested in the high vacuum level. Turn-on voltage of the uncoated tip was 35 V and maximum current was 1 mA, while turn-on voltage of the coated tip was 15 V and maximum current was 6 mA. While uncoated silicon tip was destroyed after 13 minutes after operation and showed rapid lowering of emission current, coated tip showed stable emission characteristics. Obtained currents were proved to be field emission currents using the Fowler-Nordheim plot studies.