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In this study, we perform reconfigurable n- and p-channel operations of a tri-top-gate field-effect transistor (FET) made of a p+-i-n+ silicon nanowire (SiNW). In the reconfigurable FET (RFET), two polarity gates and one control gate induce virtual electrostatic doping in the SiNW channel. The polarity gates are electrically connected to each other and program the channel type, while the control gate modulates the flow of charge carriers in the SiNW channel. The SiNW RFET features simple device design, symmetrical electrical characteristics in the n- and p-channel operation modes using p+-i-n+ diode characteristics, and both operation modes exhibit high ON/OFF ratios (∼106) and high ON currents (∼1 μA μm−1). The proposed device is demonstrated experimentally using a fully CMOS-compatible top-down processes.

This study demonstrates an optimal design method for the channel length in a p +–i–p–n + structure of feedback field-effect transistors (FBFETs) for next-generation memory devices. We demonstrate the dependence of latch-up and threshold voltages on the channel length in single-gated FBFETs with silicon channels consisting of gated and non-gated regions. The operation principle of the latch-up phenomena related to the channel length using an equivalent circuit in an FBFET has been described. The abrupt increase in the drain current of the single-gated FBFETs at the latch-up (threshold) voltage in the sweep of the drain (gate) voltage was analyzed with current gains in an equivalent circuit. The current gain depends on the gated and non-gated channel lengths; thereby, the latch-up and threshold voltages too depend on the gated and non-gated channel lengths. The dependences of the latch-up and threshold voltages on the non-gated channel length were found to be 3.62 times and 1.68 times higher than that on the gated channel length, respectively.

In this study, we design an inverter comprising a p-channel feedback field-effect transistor (p-FBFET) and an n-channel metal-oxide-semiconductor field-effect transistor and examine its logic and memory characteristics. For the transition of inverter from the logic ‘0’ (‘1’) state to ‘1’ (‘0’) state, the gain is 2001.6 V/V (1992.4 V/V). The steep switching characteristics and high on/off current ratio of the p-FBFET contribute to the high inverter gains. For an inverter with zero static power consumption, the logic states remain for more than 500 s. The long retention time allows the inverter proposed in this study to be applicable to logic-in-memory.

In this paper, we propose inverting logic-in-memory (LIM) cells comprising silicon nanowire feedback field-effect transistors with steep switching and holding characteristics. The timing diagrams of the proposed inverting LIM cells under dynamic and static conditions are investigated via mixed-mode technology computer-aided design simulation to verify the performance. The inverting LIM cells have an operating speed of the order of nanoseconds, an ultra-high voltage gain, and a longer retention time than that of conventional dynamic random access memory. The disturbance characteristics of half-selected cells within an inverting LIM array confirm the appropriate functioning of the random access memory array.

In this study, we present an optically tunable feedback field-effect transistor (FBFET) with two independent gates and a p+-i-n+ silicon nanowire. Because of the feedback operation, the FBFET features extremely steep switching characteristics with subthreshold swings alt; 4 mV/dec, and it can be reconfigured as a p- or n-type transistor by controlling the gate-voltage biases. When the FBFET is exposed to a He?Ne laser beam (? = 633 nm), photogenerated carriers accumulate in the potential wells and reduce the potential-barrier height. The optically tunable feedback operation is attributed to this lowering of the potential barrier caused by the light. The triggering voltages can be modulated according to illumination, even when feedback is being provided. This optically tunable transistor with excellent switching characteristics opens up possibilities for application in future optoelectronic devices.

In this study we investigate the influence of substrate materials on the electrical characteristics of feedback field-effect transistors (FETs) when subjected to bending fatigue. Each of our transistors are composed of a p +–i–n + doped silicon nanowire and dual-top metal gates. Feedback FETs on Ecoflex substrates feature outstanding stability compared to those on polyethersulphone and polydimethysiloxane substrates, even at a bending strain of 11.67%. The threshold voltage shift is within the range of 0.3 V, and the on-current only decreases by 15.5% (or less), when compared to the initial flat conditions. Moreover, our devices have outstanding reliability, even after 5000 cycles of repeated bending.

In this paper, we describe the feedback and tunneling operations of a dual top gate field-effect transistor (FET) with a p +-i-n + doped silicon nanowire channel. The transistor functions selectively in either a feedback FET (FBFET) or a tunneling FET mode by modulating the source-to-drain voltage, and it features an outstanding subthreshold swing characteristic of 6.15 mV dec-1 with an on/off current ratio (I on/I off) of approximately 106 in the feedback operating mode and of 41.3 mV dec-1 with I on/I off of ∼107 in the tunneling operating mode. Moreover, our device in the FBFET operation mode has memory characteristics with a retention time of 104 s and a program/erase endurance up to 103 cycles owing to the positive feedback loop in the channel region. This study demonstrates the promising potential of our devices in the development of multifunctional electronics.

Ink-jet printable Ag and Ag-Cu alloy nanoparticles were synthesized by polyol method. The conductivity of circuit fabricated by nanoparticle solutions was improved owing to optical annealing. The nanoparticles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM).

Spherical cadmium sulfide (CdS) nanoparticles, 4–5 nm in diameter, were synthesized using an aqueous cadmium nitride [Cd(NO3)24H2O] and sodium sulfide [Na2S9H2O] solution in a microemulsion system. The effects of the water to surfactant molar ratio (W = [water]/[surfactant]), the concentration of precursors, the Cd to S precursor ratio, and the density of the ultrasonic wave on the properties of the CdS nanoparticles were examined. The luminescent properties and the size effect of the nanoparticles were characterized using UV–vis absorption and photoluminescence (PL) spectra. The PL emission intensity did not change significantly with an increase in precursor and surfactant concentrations. The absorption edge and PL peak energy of the CdS nanoparticles shifted to shorter wavelengths with an increase in cadmium nitride concentration owing to a phase change and a decrease in CdS nanoparticle size.

The effect of aging on the optoelectronic properties of a single ZnO nanowire is investigated in this study. The photoluminescence (PL), photocurrent spectrum, current–voltage characteristics, and photoresponse were measured for the as-grown ZnO nanowire and for the same nanowire exposed to air for three months. For the aged nanowire, the broad PL band is weaker, the intensity of the photocurrent is stronger, and the photoresponse is slower than those of the as-grown nanowire. One of the possible explanations is that the observed aging effect on the PL is due to the reduction in the number of oxygen vacancies within the nanowire and that the aging effect on the photocurrent and photoresponse originates from the formation of oxygen vacancies near the surface.

In this study, the electronic properties of sintered HgTe nanoparticles are characterized to determine the type of charge carrier within them, and to investigate their gate effects as a function of temperature. HgTe nanoparticles synthesized by the colloidal method were first deposited on thermally oxidized Si substrates by spin-coating, and then sintered at 150 °C. The sintered nanoparticles were determined to be p-type by analyzing the drain current and drain–source voltage (Id–Vds) relationship as a function of the gate voltage (Vg). The field-effect mobilities of the holes in the sintered HgTe nanoparticles are estimated to be 0.041, 0.036, and 0.022 cm2/(Vs) at 60, 180, and 300 K, respectively. The variation in the slope of the Id–Vds curve as a function of Vg becomes more distinctive as temperature decreases. At temperatures lower than 140 K, an inversion mode was observed for the channel of the sintered nanoparticles.

In this work, the capacitance characteristics of gold nanoparticle-embedded metal–oxide-semiconductor (MOS) capacitors with Al2O3 control oxide layers are investigated. The capacitance versus voltage (C–V) curves obtained for a representative MOS capacitor embedded with gold nanoparticles synthesized by the colloidal method exhibit large flat-band voltage shifts, which indicate the presence of charge storages in the gold nanoparticles. Their hysteresis characteristics are dependent on the voltage sweep range. The clockwise hysteresis and rightward shift of the flat band voltages observed from the C–V curves imply that electrons are trapped in a floating gate layer consisting of the gold nanoparticles present between SiO2 and Al2O3 layers in the MOS capacitor, and that these trapped electrons originate from the top electrode. In addition, the characteristics of the capacitance versus time curves for the gold nanoparticle-embedded MOS capacitor are discussed in this paper.

A modified structure for tiny ultrasonic linear motors has been developed, and various shaft materials have been tested in order to improve dynamic properties. The shaft material has a direct influence on efficiency, reliability, and quality of the motors and their dynamic properties. The shaft material is crucial to achieve high performance. Shafts of with various materials, such as a stainless steel, stainless steel coated with diamond like carbon (DLC), a Pyrex, and a graphite, can make it possible to improve dynamic properties of the motors over a wide range of tribological conditions. For the motor with a stainless steel shaft coated with DLC at 47 kHz, its velocity is 6.5 mm/s and its force is 110 mN. When the motor has a Pyrex shaft, a force of 140 mN is reached at 52 kHz. Accordingly, the maximum force produced by a motor with a graphite shaft is estimated as 97 mN. The velocity of this motor was 15 mm/s. We found that graphite has a fine surface and a directional texture which can help a moving element achieve linear motion. Finally, the use of a cap resulted in significantly improving stable operation. A motor with a graphite or a Pyrex shaft showed very stable operation and improved dynamic characteristics.

Photocurrent of undoped, n- and p-type Si nanowires synthesized by thermal chemical vapor deposition is investigated in this study. For an undoped Si nanowire biased at 3 V, photocurrent excited by the 633-nm wavelength light is stronger in intensity than that excited by the 325-nm wavelength light, and photoresponses are rapid when the light is switched on and off. In contrast, for the n- and p-type Si nanowires, photocurrent excited by the 633-nm wavelength light is not measurable, although one excited by 325-nm wavelength light is still detectable. And photoresponses obtained for the doped Si nanowires are slower, compared with the undoped Si nanowire. Photocurrent phenomena observed in the undoped, n- and p-type Si nanowires are discussed in this paper.

Capacitance versus voltage (C–V) curves of Ge-nanocrystal (NC)-embedded MOS capacitors with and without a single capping Al2O3 layer are characterized in this work. C–V curves of the Ge-NC-embedded MOS capacitor with the Al2O3 layer are counterclockwise in the voltage sweeps, which indicates the presence of charge storages in the Ge NCs by the tunnelling of charge carriers between the Si substrate and the Ge NCs. In contrast, clockwise hysteresis of the C–V curves and leftward shifts of the flat band voltages are observed for the embedded MOS capacitor without the Al2O3 layer. It is suggested here that the observed characteristics of the C–V curves are due to the charge trapping at oxygen vacancies within a SiO2 layer. In addition, the illumination of the white light enhances the lower capacitance part of the C–V hysteresis. The origin for the enhancement is discussed in this paper.

The photocurrent of CdTe nanoparticles is characterized in this study to investigate the transport mechanism of charge carriers in these nanoparticles. Time-dependent photocurrent was measured while above-gap (458 nm wavelength) light was switched on and off periodically. Rapidly and slowly responding photocurrents overlapped in the time-dependent photocurrent. Our careful investigation into the time-dependent photocurrent reveals that photogenerated electrons contribute to the slowly responding photocurrent and that photogenerated holes give rise to the rapidly responding photocurrent. On the basis of our experimental results, we suggest that the transport of the photogenerated electrons takes place in the conduction band after their trapping and detrapping processes and that the photogenerated holes are transported in the valence band. In addition, time-dependent photocurrent excited by below-gap (633 nm wavelength) light, dark current, and current–voltage (I–V) loops are analyzed in this paper.

The dark current, photocurrent and photoluminescence (PL) of networked GaN nanowires were characterized in this study. GaN nanowires were synthesized from Ni particles dispersed on an alumina substrate, and subsequent Ti deposition was performed on the as-synthesized GaN nanowires to form electrodes. For the networked GaN nanowires, a significant dark current was observed and the I–V characteristics of the dark current and photocurrent were independent of temperature in magnitude and shape. These results indicate that the GaN nanowires were networked electrically between the electrodes and that the electronic states of these nanowires were degenerate. In addition, the correlation between the photocurrent and PL of the networked GaN nanowires was examined. The characteristics of the green-band emission were similar to those of the photoresponse, and the wavelength range of the green-band emission exactly overlapped that of the below-gap absorption band in the photocurrent spectra. These results indicate that the green emission and the photoresponse have a common origin.

In this study, we investigate the electrical characteristics of bendable a-Si:H thin-film transistors (TFTs) with various channel widths as a function of bending stress. Compared with a narrower channel TFT, a wider channel TFT exhibits a stable performance even at a bending strain of 1.3%. Our stress and strain distribution analysis reveals an inverse relationship between the channel width and the channel stress. As the channel width widens from 8 to 50 μm, the stress experienced by the middle channel region decreases from 545 to 277 MPa. Moreover, a 50 μm-channel-width TFT operates stably even after a 15 000 bending cycle while the 8 μm-channel-width TFT fails to operate after a 2000 bending cycle.

In this study, we propose newly designed feedback field-effect transistors that utilize the positive feedback of charge carriers in single-gated silicon channels to achieve steep switching behaviors. The band diagram, I–V characteristics, subthreshold swing, and on/off current ratio are analyzed using a commercial device simulator. Our proposed feedback field-effect transistors exhibit subthreshold swings of less than 0.1 mV dec−1, an on/off current ratio of approximately 1011, and an on-current of approximately 10−4 A at room temperature, demonstrating that the switching characteristics are superior to those of other silicon-based devices. In addition, the device parameters that affect the device performance, hysteresis characteristics, and temperature-dependent device characteristics are discussed in detail.

In this study, we propose a simple method for obtaining the thermal conductivity of silicon nanowires (SiNWs) embedded on a thermoelectric platform. The approximation of the heat flux in SiNWs with temperature differences enables the determination of thermal conductivity. Using this method, the thermal conductivities of our n- and p-type SiNWs are found to be 18.06 ± 0.12 and 20.29 ± 0.77 W m−1 K−1, respectively. The atomic weight of arsenic ions in the n-type SiNWs is responsible for a lower thermal conductivity than that of boron ions in the p-type SiNWs. Our results demonstrate that this simple method is capable of measuring the thermal conductivity of thermoelectric nanomaterials embedded on thermoelectric devices.

The electrical properties of ZnO nanowires are significantly dependent on their surface states. The surface trap charges degrade the device performance of field effect transistors. These trap charges are reduced by H2 annealing. In this work, a back-gate ZnO nanowire field effect transistor (FET) was fabricated by a photolithographic process, and its electrical properties were characterized. This back-gate FET was subsequently annealed under a flow of H2/Ar gas for 20 min. The back-gate FET annealed for 20 min exhibited remarkably enhanced electrical characteristics, as compared with the as-fabricated back-gate FET; the peak transconductance was increased from 40 to 448 nS, the field effect mobility from 27 to 302 cm2 V-1 s-1, and the Imax/Imin ratio from 1.5 to 105.

ZnO nanowire field effect transistors were fabricated on flexible substrates of poly(ether sulfone) (PES) by bottom-up and photolithographic processes and their electrical characteristics were investigated. The fabrication of the flexible devices was achieved at a processing temperature of 150 °C. A representative top-gate ZnO nanowire field effect transistor (FET) on a flexible substrate exhibits a peak transconductance of 179 nS, a field effect mobility of 10.7 cm2 V-1 s-1, and an Ion/Ioff ratio of 106. When the PES substrate is bent under a strain of 0.77%, the decrement of the drain current for the FET at VGS=10 V is less than 3%.

Single crystalline In2O3 nanowires have been synthesized by thermal evaporation of ball-milled In2O3 powders without any catalysis. The diameter and length range of the synthesized In2O3 nanowires are about 25 nm and 20–30 µm, respectively. Their X-ray diffraction pattern is indexed to bcc structure with a lattice constant of a=1.0126 nm. High-resolution transmission electron microscopy image shows that the inner part of the In2O3 nanowires is free of dislocations, and that any amorphous layers are not formed on the surface of the nanowires. In their PL spectrum, two peaks are observed in the ultraviolet region centered at 380 nm and in the visible region centered at 550 nm.

In this paper, we demonstrate the bipolar resistive switching characteristics of flexible resistive random access memory (ReRAM) devices, whose bottom electrodes are made of silicon nanowires (Si NWs) with a triangular structure, which offer preferential sites for the filaments. The temperature dependence of the low resistance state (LRS) of the resistive Al2O3/ZnO bilayers of ReRAM devices reveals that Ag filaments originating from the top Ag electrodes are responsible for bipolar resistive switching. With respect to the endurance characteristics of the LRS, resistance fluctuation is negligible because of the filaments generated at the specific sites of the vertices of the Si NW bottom electrodes. In addition, the resistive switching characteristics are maintained even after 1000 bending cycles.

In this study, a NOR-logic circuit is constructed by the vertical stacking of three individual thin-film transistors (TFTs) with the channels of solution-processed chalcogenide nanoparticle (NP) films on a plastic substrate. The NOR-logic circuit consists of two p-type HgTe NP-based TFTs, which act as drivers, and one n-type HgSe NP-based TFT, which plays the role of an active load. The logic operation is observed with a substantial difference in Vout between the logic state of "00" and the other logic states, and the logic swing is ~60%.

High performance NOT, NAND and NOR logic gates composed of GaAs-nanowire (NW)-based metal‐semiconductor field-effect transistors (MESFETs) were constructed on flexible plastics through a noble top-down route. The representative GaAs-NW-based MESFETs exhibited superior electrical characteristics such as a high mobility (∼3300 cm 2 V −1 s −1 ), large Ion/Ioff ratio (∼10 8 ) and small subthreshold swing (∼70 mV/dec). The NOT, NAND and NOR logic gates showed a maximum voltage gain of 108 and logic swings of 97‐99%. All of the logic gates successfully retained their electrical characteristics during 2000 bending cycles. Furthermore, the logic gates were well operated by square-wave signals of up to 100 MHz under various strain conditions. The high performances demonstrated in this study open the way to the realization of high speed flexible logic devices. (Some figures may appear in colour only in the online journal)

Top-gate field-effect transistors (FETs) based on triangular silicon nanowires (SiNWs) obtained from a silicon bulk wafer using a conventional silicon manufacturing technology are constructed on flexible plastic substrates. Their field-effect mobility and peak transconductance are enhanced by 10% in the upwardly bent state and by 29% in the downwardly bent state at a strain of 1.02%, compared with the flat state. The strain effect resulting from the bending of the flexible substrates is higher in the downward state than in the upward state, and the increase in strain improves the performance of SiNW-based FETs. Moreover, their device performance is stable even after bending the substrate several thousand times.

The optical characteristics of an n-type ZnO/p-type Si crossed nanowire (NW) light-emitting diode (LED) were investigated in this study. N-ZnO nanowires (NWs) were synthesized by thermal chemical vapor deposition, and p-Si NWs were fabricated by etching a single crystalline Si wafer. The p–n heterojunction LED formed by the cross of the n-ZnO and p-Si NWs selected from the NWs prepared in this work exhibited the current rectifying behavior with the turn-on voltage of 1.3 V. Our investigation of the photoluminescence spectrum of the as-grown n-ZnO NWs and electroluminescence spectrum of the n-ZnO/p-Si crossed NW LED reveals that both spectra have the same position of peaks at 390 nm. This result indicates that the UV emission from the crossed NW LED is mostly attributed to the band-to-band transition of electrons in the ZnO NW.

The optoelectronic characteristics of HgSe nanoparticle films spin-coated on plastic substrates are investigated in this work. The photocurrent of a representative HgSe nanoparticle film under the illumination of 633-nm wavelength light is 10 times larger than the dark current in air at room temperature. In addition, the effects of bending on the optoelectronic characteristics of the HgSe nanoparticle film are examined by applying tensile and compressive strains to the plastic substrate.

The simple type conversion of n-type silicon nanowires (SiNWs) to p-type by the diffusion of Au ions is demonstrated in this study. An Au thin film with a thickness of 10 nm was thermally deposited on an n-type SiNW and a rapid thermal annealing process was performed subsequently to diffuse the Au ions into the SiNW. The electrical characteristics of a back-gate field-effect transistor with a channel composed of the Au-diffused SiNW show that the Au-diffused SiNW acts as a p-type one. The type conversion phenomenon of the SiNW caused by the diffusion of Au ions is discussed in detail in this paper.

Flexible electronic devices which are lightweight, thin and bendable have attracted increasing attention in recent years. In particular, solution processes have been spotlighted in the field of flexible electronics, since they provide the opportunity to fabricate flexible electronics using low-temperature processes at low-cost with high throughput. However, there are few reports which describe the characteristics of electronic devices on flexible substrates. In this study, we fabricated flexible thin-film transistors (TFTs) on plastic substrates with channel layers formed by the spin-coating of ZnO nanoparticles and investigated their electrical properties in the flat and bent states. To the best of our knowledge, this study is the first attempt to fabricate fully functional ZnO TFTs on flexible substrates through the solution process. The ZnO TFTs showed n-channel device characteristics and operated in enhancement mode. In the flat state, a representative ZnO TFT presented a very low field-effect mobility of 1.2 x 10(-5) cm(2) V(-1) s(-1), while its on/off ratio was as high as 1.5 x 10(3). When the TFT was in the bent state, some of the device parameters changed. The changes of the device parameters and the possible reasons for these changes will be described. The recovery characteristics of the TFTs after being subjected to cyclic bending will be discussed as well.

A technique to implement silicon nanowire (SiNW)-based tunneling field-effect transistors (TFETs) on flexible plastic substrates is developed for the first time. The p-i-n configured Si NWs are obtained from an Si wafer using a conventional top-down CMOS-compatible technology, and they are then transferred onto the plastic substrate. Based on gate-controlled band-to-band tunneling (BTBT) as their working principle, the SiNW-based TFETs show normal p-channel switching behavior with a threshold voltage of -1.86 V and a subthreshold swing of 827 mV/dec. In addition, ambipolar conduction is observed due to the presence of the BTBT between the heavily doped p+ drain and n+ channel regions, indicating that our TFETs can operate in the n-channel mode as well. Furthermore, the BTBT generation rates for both the p-channel and n-channel operating modes are nearly independent of the bending state (strain = 0.8%) of the plastic substrate.

The photocurrent characteristics of HgTe nanoparticle (NP) thin films fabricated on glass substrates were investigated under the illumination of 1.3 ?m wavelength light in this work. The photocurrent obtained from an NP thin film with a vertical structure was 119 ?A in magnitude at an applied voltage of 2 V. The magnitude of the photocurrent for an NP thin film with a lateral structure was 23.8 nA at 10 V. Nevertheless, the relative magnitude of the photocurrent measured as a function of the chopping frequency was largely the same for the thin films with both the lateral and the vertical structures. The frequency-dependent photocurrent mechanism of the NP thin films will be discussed in detail in this paper.

Undoped, Mn-doped, Pr-doped, and Mn- and Pr-codoped ZnS nanoparticles were synthesized by a wet chemical method, and these nanoparticles were optically annealed in air or vacuum. In the photoluminescence (PL) spectra of the optically annealed nanoparticles, a sulfur–vacancy-related PL band at around 420 nm, a PL band associated with the 4T1→6A1 transition of Mn2+, and PL peaks associated with Pr-related complexes were investigated during optical annealing. The integrated PL intensities for the nanoparticles annealed in air increased more markedly with the optical annealing time than those for the nanoparticles annealed in vacuum. This increase may be explained by the photooxidation of the surface, the enhancement of the crystal quality, and the gradual diffusion of luminescent ions into the crystal lattice.

The effects of rapid thermal annealing (RTA) on Co/p-GaN contacts in an O2/N2 atmosphere without intermediate metal were investigated. It was observed that the contact resistance (ρc) decreased with increasing RTA temperature and that the resistance was reduced by a factor of about 30 after RTA at 600°C in the O2/N2 atmosphere. The specific minimum contact resistance was in the 10-2 Ω·cm2 range. Comparison of the R 0 and ρc values revealed that the rapid thermal annealing in the O2/N2 was more effective for reducing the contact resistance than conventional furnace annealing. The reason for the reduction of resistance was expected to be the increase of hole concentration due to the highly reactivated removal of hydrogen atoms in the p-GaN by RTA in the O2/N2 atmosphere.

The luminescence properties of III–V nitride films (an undoped GaN, an undoped GaN/Al0.2Ga0.8N multiquantum well, and a p-type Mg-doped GaN films) were investigated using the depth-resolved cathodoluminescence (CL) spectroscopy. From the low- and room-temperature CL of the undoped GaN and GaN/AlGaN MQW films, an emission at 2.9 eV was found with the longer penetration depth and is attributed to the higher density of dislocations at the interface between the film and the substrate. In order to explain the depth-resolved CL of the Mg-doped GaN film, the configuration coordinate model is proposed on the basis of the local strain near the Mg impurities. This model demonstrates that local strain may play a crucial role in controlling the radiative efficiency, line width, and peak position of the luminescence from the film.

The optical transmission, temperature-dependence of the photoluminescence (PL), and Raman scattering of porous SiC prepared from p-type 6H-SiC are compared with those from bulk p-type 6H-SiC. While the transmission spectrum of bulk SiC at room temperature reveals a relatively sharp edge corresponding to its band gap at 3.03 eV, the transmission edge of porous SiC (PSC) is too wide to determine its band gap. It is believed that this wide edge might be due to surface states in PSC. At room temperature, the PL from PSC is 20 times stronger than that from bulk SiC. The PL PSC spectrum is essentially independent of temperature. The relative intensities of the Raman scattering peaks from PSC are largely independent of the polarization configuration, in contrast to those from bulk SiC, which suggests that the local order is fairly random.

Direct transport measurement results of an InAs self-assembled quantum dot system have been reported. The differential conductance characteristics measured from the metal-semiconductor-metal diodes incorporating InAs self-assembled quantum dots show conductance peaks. The energy spectrum of the dots is obtained from the peak positions.