Satoshi Abo

Local resistance measurement across grain boundaries in low-temperature polycrystalline silicon layer of thin film transistor using scanning spreading resistance microscopy

Local resistance distribution in a low-temperature polycrystalline Si layer of a thin film transistor with a lightly doped drain (LDD) structure was investigated using scanning spreading resistance microscopy. The local resistance around the grain boundaries was found to be lower than that at grain insides in the drain, LDD, and channel regions. At the center of the grain boundaries, however, slightly higher resistance part was sandwiched between low resistance regions. Identifying the drain, the LDD, and the channel regions is succeeded by an analysis in which only the lower local resistances were used.

Transport Properties of Beam-Deposited Pt Nanowires

Pt wires were fabricated by using electron-beam (EB) and Ga focused-ion-beam (FIB) irradiation while providing C5H5Pt(CH3)3 gas through a nozzle. Electron transport properties of the wires were investigated. The resistance of the EB-deposited wires was quite high as deposited but was reduced by 3-4 orders of magnitude after 400-500°C annealing. The electron transport of the as-deposited EB-deposited wire was dominated by the variable range hopping and the Coulomb blockade simultaneously, and showed the antilocalization effect after 400°C annealing. The electron phase-breaking length in the EB-deposited wire with 400°C annealing, which was derived from a theoretical fitting, is ≈10 nm at ≈4 K and increases with decreasing temperature. This means that 10-nm fabrication technology and improvement of coherence length are required for coherent vacuum nanoelectronics.

Development of planar x-ray source using gated carbon nanotube emitter

A planar x-ray source using gated carbon nanotube (CNT) emitters was developed. In the diode structure measurement, the turn-on electric field of the CNT cathode was approximately 1.2 V/μm. In the triode structure measurement, characteristic x-ray peaks of Cu and bremsstrahlung x-rays were observed. The maximum energies of the bremsstrahlung x-rays were in agreement with anode voltages. Pulse x-rays synchronized with pulsed gate voltages. Clear x-ray transmission images with high spatial resolution ≤165 μm were obtained.

Electron emission from LiNbO3 crystal excited by ultraviolet laser

X-ray generation by a thermally heated LiNbO3 crystal and effect of ultraviolet (UV) laser light irradiation to a LiNbO3 crystal on pyroelectric electron emission were investigated. The x ray was detected with a gap distance of 15 mm between the surface of the crystal and the anode, whereas it was not detected with a gap distance of ∼200 μm. The dependence of the electron emission excited by UV laser irradiation on the vacuum pressure, laser power density, and gap distance between the crystal and the anode was measured. The electron emission showed a fast response with a rise time of 1 μs to the laser irradiation. The emission current was 45 nA with a laser power density of 6.6 MW/cm2 with a gap distance of 125 μm between the surface of the crystal and the anode.

Fabrication and electron field-emission properties of titanium oxide nanowire on glass substrate

Titanium-oxide nanowires, whose diameter and length were in the order of 10 nm and 1 μm, respectively, were successfully fabricated directly on a glass substrate. The fabrication process adopted is very simple, in which the sputter-coated titanium film was immersed into NaOH solution at 80 °C and annealed at 500 °C in vacuum. Field-emission current from the titanium-oxide nanowires synthesized on a glass substrate was first observed, whose turn-on field was approximately 4 V/μm.

Maskless laser processing of graphene

Display Omitted Graphene on a SiO2/Si substrate was removed by UV pulsed laser irradiation.Threshold laser power density to remove graphene depended on the graphene thickness.The mechanism is discussed using kinetic energy of thermal expansion.Thickness (or layer-number) selective process for graphene is demonstrated.Maskless patterning of graphene using laser irradiation in the air is demonstrated. Graphene on a SiO2/Si substrate was removed by ultraviolet pulsed laser irradiation. Threshold laser power density to remove graphene depended on the graphene thickness. The mechanism is discussed using kinetic energy of thermal expansion of the substrate surface. Utilizing the thickness dependence, thickness (or layer-number) selective process for graphene is demonstrated. Maskless patterning of graphene using laser irradiation in the air is also demonstrated.

Effects of carbon nanotube diameters of the screen printed cathode on the field emission characteristics

Carbon nanotubes (CNTs) with diameters of 10 or 100 nm have been screen printed on indium tin oxide/glass substrates and treated by an adhesive tape or a KrF excimer laser. After the surface treatment, the field emission characteristics of CNT cathodes have been measured. The lower turn-on electric fields have been obtained for the CNT cathodes with a CNT diameter of 10 nm. Then a high electric field pulse aging has been performed to get more uniform emission images. Finally, the field emission lifetimes of CNT cathodes have been measured. The lifetimes of the CNT cathodes treated by tape peeling have been only several hours at a dc measurement, whereas the lifetimes of the CNT cathodes treated by a KrF excimer laser, regardless of the CNT diameter, reached 100 h, corresponding to 100 000 h at a duty ratio of 1/1000.

Development of enhanced depth-resolution technique for shallow dopant profiles

Abstract A rapid shrinkage in the minimum feature size of integrated circuits requires analysis of dopants in their shallow source–drain and their extensions with an enhanced depth resolution. Rutherford backscattering spectroscopy (RBS) combining a medium-energy He ion beam with a detector of improved energy resolution should meet the requirement of a depth resolution better than 5 nm at a depth of 10–20 nm in the next 10 years. A toroidal electrostatic analyzer of 4×10−3 energy resolution has been used to detect the scattered ions of a medium-energy He ion beam. Five keV As+ implanted Si or SiO2 samples were measured. Depth profiling results using the above technique are compared with those of glancing-angle RBS by MeV energy He ions. Limitations in the energy resolution due to various energy-spread contributions have been clarified.

X-ray source using carbon-nanotube field emitter with side-gate electrode

A carbon-nanotube (CNT) field emitter with side-gate electrodes, which are placed in-plane with the CNT emitters, is one of the most promising structures to realize a large-area X-ray charge neutralizer with a cost-effective and easy process. An X-ray source using the screen-printed CNT field emitter with side-gate electrodes is developed. The field-emission and X-ray properties are evaluated with anode voltages of 5 and 10 kV. It is shown that the emission current can be controlled by the side-gate voltage even with such high anode voltages as 5 and 10 kV. It is reported that the highest anode current is approximately 1 µA, which is high enough for an X-ray charge neutralizer. The X-ray radiation is successfully controlled by the pulsed side-gate voltage with subsecond length.

Effect of electron focusing in x-ray sources using LiTaO3 crystals excited by neodymium-doped yttrium lithium fluoride laser light

The intensity of x-rays from a 15 mm-diameter metal target bombarded by electrons emitted from a LiTaO3 crystal is found to depend upon the distance, h, between the crystal and the target. The electron emission of the LiTaO3 crystal is generated by being excited with light from a neodymium-doped yttrium lithium fluoride laser. The x-ray intensity is highest for h = 6 mm, coinciding also with a minimum electron spot size. The coincidence of the minimum electron spot size and maximum x-ray intensity with the 15 mm-diameter target is a result of self-focusing of the electrons by the higher electric field at the edge of the cylindrical crystal. The maximum electron energy at h = 6 mm with 120 s of laser irradiation is 47 keV, which is estimated from the maximum energy of bremsstrahlung x-rays.