Zainal Arif Burhanudin

Thermal Agglomeration of Ultrathin Silicon-on-Insulator Layers: Crystalline Orientation Dependence

The thermal agglomeration of ultrathin silicon-on-insulator (SOI) layers with different crystalline orientations [(110)-, (100)-, and (111)-oriented SOI layers] is reported. (110) SOI agglomeration leads to the formation of Si island arrays along and directions, while (100) and (111) SOI agglomerations result in Si island arrays in directions and Si wires in directions, respectively. The {311} facets mainly determine the direction of the agglomerated shape, whereas the symmetric and asymmetric facet properties are responsible for Si island and wires formation, respectively. These results indicate that Si islands or wires can be formed in certain directions by selecting the appropriate SOI crystalline orientation.

Breakdown voltage reduction by field emission in multi-walled carbon nanotubes based ionization gas sensor

Ionization gas sensors using vertically aligned multi-wall carbon nanotubes (MWCNT) are demonstrated. The sharp tips of the nanotubes generate large non-uniform electric fields at relatively low applied voltage. The enhancement of the electric field results in field emission of electrons that dominates the breakdown mechanism in gas sensor with gap spacing below 14 μm. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7 μm gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed.

A review of nanostructured based radiation sensors for neutron

Currently radiation sensors with various mechanisms such as radio thermo luminescence, radiographic and radiochromic film, semiconductor and ionization have been used for the detection of nuclear radiation. Sensitivity, handling procedure, heating condition, energy response, nonlinearity, polarization, non-uniform electric field, high bias voltage and spatial resolution due to large physical size are some of the key issues faced by these sensors. Due to the excellent electrical and mechanical properties, nanostructured materials such as carbon nanotubes (CNTs) have been researched as sensing elements in the sensors to overcome the mentioned problems. However CNTs are found to pose different problems, arising from the uncontrolled helicity and small cross-sectional area. Therefore, alternative sensing elements are still been sought after and the possibility of using boron nitride nanotubes for sensing neutron is considered in this review.

Detection of field-induced single-acceptor ionization in Si by single-hole-tunneling transistor

The authors have detected the ionization of single-acceptors in the underlying p on p+ substrate of a silicon-on-insulator (SOI) wafer using a single-hole-tunneling (SHT) transistor fabricated in the top Si layer of the SOI at low temperatures. It was found that freeze-out boron atoms in the substrate are sequentially ionized from near the buried SiO2∕p-Si substrate interface to deeper positions by application of a vertical electric field, creating steplike features in the time-dependent SHT current.

Thermally-induced formation of Si wire array on an ultrathin (111) silicon-on-insulator substrate

We have found that a Si wire array is formed by thermal agglomeration of an ultrathin (111) Si layer in a bonded silicon-on-insulator (SOI) structure, although previous studies for crystalline and amorphous Si layers on SiO2 only showed island formation. As starting material, (111) bonded SOI wafers with the top Si layers thinned to 5–9 nm were used. The samples were then subjected to a thermal treatment at 950 °C in an ultrahigh vacuum. Atomic force microscopy revealed that the (111) top Si layer is deformed into three sets of wire arrays in the three equivalent ⟨112¯⟩ directions. It is also shown that the patterning of a Si layer leads to the wire array selectively formed in one of these three directions.

Effect of electrode gap on the sensing properties of multiwalled carbon nanotubes based gas sensor

Vertically aligned multiwalled carbon nanotubes (MWCNT) were grown on Si substrate coated with alumina and iron using chemical vapor deposition. Electrode gap of 10, 25 and 50 µm were adopted to determine the effect of varying gap spacing on the sensing properties such as voltage breakdown, sensitivity and selectivity for three gases namely argon, carbon dioxide and ammonia. Argon has the lowest voltage breakdown for every electrode gap. The fabricated MWCNT based gas sensor drastically reduced the voltage breakdown by 89.5% when the electrode spacing is reduced from 50 µm to 10 µm. The reduction is attributed to the high non-uniform electric field between the electrodes caused by the protrusion of nanotips. The sensor shows good sensitivity and selectivity with the ability to detect the gas in the mixture with air provided that the concentration is ≥ 20% where the voltage breakdown will be close to the pure gas.

Effect of reaction time on the characteristics of catalytically grown boron nitride nanotubes

The paper reports on the growth of boron nitride nanotube (BNNTs) on Si substrate by catalytic chemical vapor deposition technique and the effect of reaction time and temperature on the size and purity were investigated. Scanning electron microscopy image revealed the bamboo-like BNNTs of multiwalled type with interlayer spacing of 0.34 nm. EDX analysis described the presence of a small percentage of Mg in the sample, indicating the combination of base-tip growth model for the sample synthesized at 1200°C. The reaction time has an effect of extending the length of the BNNTs until the catalyst is oxidized or covered by growth precursor.

Si Single-Electron SOI-MOSFETs: Interplay with Individual Dopants and Photons

We have demonstrated that Si single-electron or single-hole SOI-MOSFETs with the multi-dots channel have attractive new functions such as photon detection and single-electron transfer. Multi-dots formed by selective-oxidation-induced patterning of the thin SOI layer have been used in the experiments of photon detection, while, most recently, we have utilized smaller dots consisting of individual dopant potentials in single electron transfer devices. Furthermore, in order to directly observe spatial landscape of single charges in the channel region, we have developed Low Temperature-Kelvin Probe Force Microscopy and succeeded in detecting single-dopant potential in the channel region. In this paper, photon detection by these devices will be primarily described.

“Manipulation of single-electrons in Si nanodevices

Recently, we are entering a new stage of electronics, in which time-controlled transport of individual electrons can be achieved by using nanodevices, so-called single-electron tunneling devices. Also, it is recognized that single-electron transport is highly sensitive to ultimately small environmental charges such as a photogenerated electron and a doped ion, leading to a new paradigm in electronic devices working with a few elemental particles, i.e., electrons, phonons and ions.