Tomomi Yoshimoto

A High Current Gain Si Metal Insulator Semiconductor Tunnel Emitter Transistor

A Si metal insulator semiconductor tunnel emitter transistor (Si MIS TET) was fabricated and investigated. The current gain of the Si MIS TET with a 32 A SiO2emitter barrier was 76 at 300 K and 74 at 100 K. It was confirmed that the inversion base layer indeed functioned as a base of the Si MIS TET.

Emission Properties from Carbon Nanotube Field Emitter Arrays (FEAs) Grown on Si Emitters

Electron emission properties of carbon nanotube field emitter arrays (CNT FEAs) having carbon nanotube emitters on the top of Si emitters were investigated under the ultrahigh-vacuum (UHV) condition. The emission pattern from the CNT FEAs was confirmed on a phosphor screen. The emission current followed the Fowler-Nordheim relationship under the high emission current condition. With the emission current of 0.5 mA, the fluctuation of the emission current was 3% or lower at the background pressure of ~ 10-7 Pa.

Field-emission characteristics from carbon nanotube field emitter arrays grown on silicon emitters

The fluctuation of the emission current from carbon nanotube field emitter arrays (CNT FEAs) grown on silicon emitters was investigated as a function of total emission current and ambient pressure. The ratio of amplitude of short-term fluctuation ΔI and average emission current Iave strongly depended on Iave. The relationship ΔI/Iave∝Iave−1/2 was found. This relationship showed that the average emission current Iave is proportional to the number of active carbon nanotube emitters. The effect of vacuum pressure on the emission properties was examined by adjusting the pumping speed of the turbomolecular pump. The emission current at fixed voltage was affected by the adsorption of gas species and amounts.

Field emission from diamond micropowders with sharp edges

The authors examined the field emission from diamond micropowders with sharp edges whose current followed the Fowler–Nordheim relationship, and confirmed that the micropowders functioned as field emission sources. In addition, the fluctuation in emission current improved as the current was increased. The emission current was constant at pressures ranging from 10−6 to 10−3 Pa under a fixed applied voltage.

Temperature Dependence of Field-Emission Characteristics from a p-Type Si Single Emitter with Real Surface

The temperature dependence of field-emission current from a p-type Si single emitter with a real surface was investigated. The field emission pattern of the emitter did not show any symmetry which indicates a clean crystal structure of the surface; however, the highly nonlinear characteristics in log (I/V2) vs 1/V plots (F-N plots) commonly observed from a clean p-type Si emitter are obtained. The emission current at the gentle slope region of F-N plots (Isat) shows strong temperature dependence at a fixed applied voltage. The slope of log Isat vs 1/T plots gives an activation energy of 0.58 eV. The most probable conclusion is that the Fermi level is pinned at the middle of the band gap of the surface and electrons generated from the surface state to the conduction band are emitted.

Field Emission from Silicon Carbide (SiC) Micropowders

Field emission characteristics of a cathode consisting of SiC micropowders with sharp edges were examined. Emission current from the cathode followed the Fowler–Nordheim relationship; therefore, it was confirmed that the SiC micropowders acted as the field electron source. A field enhancement factor of ~1000 was obtained. This value was comparable to that of conventional emitters. A good short-term stability of the fluctuation in the emission current from the cathode, which was less than 7% of the total emission current, was determined.

Ionized cluster beam deposition of antimony and bismuth films

The structure of antimony and bismuth thin films grown on glass or Si(001) substrates by ionized cluster beam (ICB) deposition was characterized. X-ray diffraction measurements were carried out to investigate the structures of the films. The dependence of the crystalline orientation in antimony films grown on the glass substrate on the applied voltage was observed. With increasing applied voltage, the x-ray diffraction peaks from the planes become weak and those from the planes become relatively strong. In bismuth films deposited on the Si(001) substrate at , the dominant crystal face is the (012) plane. These results show that the crystalline orientation of antimony and bismuth films can be controlled well according to the applied voltage and substrates used in the ICB deposition.

Si Metal Insulator Semiconductor Tunnel Emitter Transistor (Si MIS TET)

A Si metal-insulator-semiconductor tunnel emitter transistor which has quite a thin base layer formed by an inversion hole layer was fabricated. A common emitter current gain of 5 was obtained at room temperature. The emitter base bias at which the base current began to flow coincided well with the calculated turn on voltage at which the inversion occurred in the MIS structure. It was confirmed for the first time that the inversion hole layer really worked as the base of the transistor.

Integration of a GaAs SISFET and GaAs inversion-base bipolar transistor

The first integration of a GaAs FET-type device and a GaAs bipolar transistor-type device was achieved using the GaAs SISFET and GaAs inversion-base bipolar transistor (GaAs IBT). The GaAs SISFET showed the transconductance of gm=80 mS/mm and 190 mS/mm at 300 K and 77 K, respectively. The GaAs IBT showed the current gain of β=18 and 13 for the common emitter configuration at 300 K and 77 K, respectively.

Field-Emission Characteristics of Carbon Nanotube Single Tip Grown on Si Cone

The field-emission characteristics of a carbon nanotube single tip were investigated as functions of annealing temperature. The current–voltage (I–V) characteristics (linearity of Fowler–Nordheim plots as well as emission pattern) were altered by annealing in the temperature range from 470 to 1270 K. On the other hand, the voltages required for the same emission current were relatively unaltered. The emission current showed little dependence on the temperature of the carbon nanotube (CNT) single tip. The fluctuation of the emission current was markedly improved by increasing the annealing temperature.