Tokishige Banno

Fabrication of diamond single-hole transistors using AFM anodization process

Abstract By the field-assisted local anodization technique using an atomic force microscope (AFM), a single-hole transistor has been fabricated on an undoped hydrogen-terminated diamond surface where p-type conduction occurs on the subsurface region. A dual side-gated FET structure has been applied to modulate the island potential in the single-hole transistor. The island size is 230 nm×230 nm, and the width of the barrier is approximately 100 nm. Measurements of the current–gate voltage characteristic at a temperature of 4.6 K show significant non-linearities including a current oscillation suggestive of single-hole transistor behavior. The oscillation that is significantly affected by the application of the side gate potential is explained by the shrinkage of the conductive island with the expansion of the depletion region.

Fabrication of single-hole transistors on hydrogenated diamond surface using atomic force microscope

Nanofabrication of electron devices based on the stability of hydrogen- and oxygen-terminated diamond surfaces is performed using an atomic force microscope modification technology. A nanotechnology involving the separation of C–H and C–O bonded surfaces has been applied to realize the single-hole transistors. The single-hole transistors operate at liquid-nitrogen temperature (77 K), where the Coulomb oscillation characteristics are clearly observed.

Memory effect of diamond in-plane-gated field-effect transistors

A memory effect of in-plane-gated field-effect transistors (IPGFETs) has been observed on hydrogen-terminated and oxygen-terminated diamond surfaces. The hysteresis characteristics are achieved by the hole traps in the oxygen-terminated surface of the IPGFETs where the threshold voltage shift by the gate voltage sweep is confirmed in the Id–Vg characteristics. This feature is observed under light illumination, and depends on the radiant flux density. The hysteresis characteristics become very small under the condition of no light irradiation at room temperature. It is assumed that carrier trap sites on the insulating part of IPGFET cause the hysteresis characteristics. Radiant flux enhances carrier migration.

Fabrication of diamond in-plane-gated field effect transistors using oxygen plasma etching

Abstract Diamond dual in-plane-gated field effect transistors with very low gate leakage current have been fabricated on an undoped hydrogen-terminated diamond p-type surface using oxygen plasma etching. Adjusting the threshold voltage optimally by one side gate, lateral electric field from the other side gate modulates the channel conductance. The oxygen plasma etching of 60 nm in depth fully isolated the channel of the hydrogen-terminated diamond surface conductive layer from the side gates resulting very low gate leakage current (

Investigation of Current-Voltage Characteristics of Oxide Region Induced by Atomic Force Microscope on Hydrogen-Terminated Diamond Surface

The current-voltage characteristic of the atomic force microscope (AFM) field-assisted local oxidized region on an undoped hydrogen-terminated (H-terminated) diamond surface is investigated. The barrier height on the top of the valence band between the undoped H-terminated diamond surface and the AFM oxidized surface is estimated by Fowler-Nordheim (F-N) tunneling current analysis. By fitting the parameter of the slope in the F-N plot, the barrier height is estimated to be 61 meV in the electrically isolated conductive island structure. On the other hand, the barrier height is also estimated to be 72 meV in the lateral tunneling diode.

Nanodevice Fabrication on Hydrogenated Diamond Surface Using Atomic Force Microscope

Abstract : Nanofabrication on a hydrogen-terminated diamond surface is performed using an atomic force microscope (AFM) anodization. Locally insulated areas less than 30 nm are successfully obtained. Side-gated field effect transistors (FETs) are fabricated using the local anodization, and they operate successfully. Single hole transistors composed of one side-gated FET and two tunneling junctions are also fabricated and operate at liquid nitrogen temperature (77 K).

Cryogenic operation of diamond surface-channel electronic devices

and so on. To investigate the carrier behavior of the surface conductive layer at low temperature, and to elucidate the mechanism of the surface conductive layer, we demonstrated the low-temperature (4.4 K) operation of the diamond FETs. Moreover, we also fabricated in-plane-gate FET structure and in-plane-gate single-electron transistor on diamond surface, and cryogenic operations are performed. DC characteristics of a 5 pm-gate Cu/CaF2ldiamond MISFET are shown in Fig. l. FET operates successfully at cryogenic temperature, even though the carrier freeze-out below the specific critical temperature was reported in diamond surface conductive layer [2]. In the DC characteristic at 4.4 K, drain current suppression occurs at V6s:0, which is related to the carrier fteeze out. However, in the FET structure, carrier can be induced by the sufficient field effect (field effect doping). In the low-temperature characteristics, we have to consider the drain threshold voltage which appears at Vns-0.3V. This is due to the energy barrier existing between the source/drain electrode and the surface conductive layer. At 300 K, caniers have enough thermal energy to overcome such barrier. However, at low temperatures, this small potential barrier is higher than thermal energy of carriers. This barrier is remarkably reduced by the longitudinal elechic field that results from the drain bias Vos. Diamond is a promising semiconductor material for the future electronics. Owing to its high break down field (107 V/cm), extremely high thermal conductivity (20 WcmK), high hote mobility (1800 r*t/Vs) and low dielectric constant (5.7), diamond is expected as a candidate for high power, high-frequency devices. However, room temperature device operation is still problematic in impurity-doped (boron for p-type, phosphorus or sulfur for n-type) diamond due to their deep activation energy. In that sense, hydrogen-terminated diamond is attractive for electrical applications because it induces p-type surface conduction even if the diamond is not intentionally doped. Up to now, the fabrication and the operation of MESFETs and MISFETs have been demonstrated using a surface conductive layer [1]. On the other hand, cryogenic operation of the semiconductor devices is an interesting issue not only for studying the physical properties of semiconductor materials and devices, but also for practical aspects. Expected advantages of low temperature operation of electronic systems are higher device performance because of increased carrier mobility and saturation velocity, lower power dissipation because of the sharper turn-on characteristics of FETs, reduced thermally activated degradations of the device performance