A Highly Transparent Artificial Photonic Nociceptor

A nociceptor is an essential element in the human body, alerting us to potential damage from extremes in temperature, pressure, etc. Realizing nociceptive behavior in an electronics device remains a central issue for researchers, designing neuromorphic devices. This study proposes and demonstrates an all‐oxide‐based highly transparent ultraviolet‐triggered artificial nociceptor, which responds in a very similar way to the human eye. The device shows a high transmittance (>65%) and very low absorbance in the visible region. The current–voltage characteristics show loop opening, which is attributed to the charge trapping/detrapping. Further, the ultraviolet‐stimuli‐induced versatile criteria of a nociceptor such as a threshold, relaxation, allodynia, and hyperalgesia are demonstrated under self‐biased condition, providing an energy‐efficient approach for the neuromorphic device operation. The reported optically controlled features open a new avenue for the development of transparent optoelectronic nociceptors, artificial eyes, and memory storage applications.     

Extremely scaled 3-dimensional multiple-gate technologies for terabit era

In order to make possible silicon-based, room-temperature operable devices having a feature size in the sub-5 nm range, an all-around gate FinFET having an extremely narrow gate-surrounded silicon fin with a floating body was proposed and fabricated. Sub-10 nm device issues such as short channel effects, punchthrough, source/drain series resistance, gate misalignment, and hot-carrier injection were intensively studied and optimized for the sub-5 nm structure. The sub-5 nm all-around gate FinFET with 3 nm fin width and 1.2 nm EOT was demonstrated for the first time.     

Bioelectronic Skin Based on Nociceptive Ion Channel for Human‐Like Perception of Cold Pains

A bioelectronic skin device based on nociceptive ion channels in nanovesicles is developed for the detection of chemical cold‐pain stimuli and cold environments just like human somesthetic sensory systems. The human transient receptor potential ankyrin 1 (hTRPA1) is involved in transmission and modulation of cold‐pain sensations. In the bioelectronic skin, the nanovesicles containing the hTRPA1 nociceptive ion channel protein reacts to cold‐pain stimuli, and it is electrically monitored through carbon nanotube transistor devices based on floating electrodes. The bioelectronic skin devices sensitively detect chemical cold‐pain stimuli like cinnamaldehyde at 10 fm , and selectively discriminate cinnamaldehyde among other chemical stimuli. Further, the bioelectronic skin is used to evaluate the effect of cold environments on the response of the hTRPA1, finding that the nociceptive ion channel responds more sensitively to cinnamaldehyde at lower temperatures than at higher temperatures. The bioelectronic skin device could be useful for a basic study on somesthetic systems such as cold‐pain sensation, and should be used for versatile applications such as screening of foods and drugs.     

Channel width and length dependence in Si nanocrystal memories with ultra-nanoscale channel

The use of nanoscale channel MOSFETs as a candidate for future nonvolatile memory is extensively investigated. The device consists of a wire channel MOSFET with nanometer dimensions on which Si nanocrystals (Si-NCs) are deposited. The memory characteristics as a function of the channel widths for different channel lengths are presented. The channel length dimensions are defined between 100-1000 nm by electron beam lithography and the width dimensions are reduced from a few tens of nanometers down to sub-5 nm by wet etching and thermal oxidation processes. It is found that the controllability of the fabrication process is enhanced as the channel length is reduced to 100 nm. Moreover, memory performances are improved with decreasing channel width due to the bottleneck effect. These results show that the Si-NCs memory is highly scalable in terms of the channel size. In the narrowest channel devices, i.e., in the sub-5-nm range, coulomb-blockade oscillations are obtained due to the ultra-small regions formed in the channel. In such devices, a strong enhancement of the retention characteristics has been found as a result of the quantum mechanical narrow channel effect in the ultra-narrow channel.     

Sub-10 nm self-enclosed self-limited nanofluidic channel arrays

We report a new method to fabricate self-enclosed optically transparent nanofluidic channel arrays with sub-10 nm channel width over large areas. Our method involves patterning nanoscale Si trenches using nanoimprint lithography (NIL), sealing the trenches into enclosed channels by ultrafast laser pulse melting and shrinking the channel sizes by self-limiting thermal oxidation. We demonstrate that 100 nm wide Si trenches can be sealed and shrunk to 9 nm wide and that lambda-phage DNA molecules can be effectively stretched by the channels.     

Influence of the epitaxial growth and device processing on the overlay accuracy during processing of the d-DotFET

To maintain the development of MOSFET devices in the last three decades the lateral layout of this important device was scaled down into the sub-50 nm range. The challenge to maintain device performance was met by applying to scaling rules, which ensure a proper physical behaviour in the active area of the device. But nowadays new device architectures as Ultra Thin Body and Multi Gate devices have to be discussed. Furthermore new materials were introduced as high-κ gate dielectrics and metal gates. In recent years strained silicon has drawn increasing attention to enlarge carrier mobility in the MOSFET channel. In the d-DotFET approach locally strained silicon is formed by means of template-assisted self assembly of Ge-dots and silicon overgrowth. The silicon capping layer is strained on top of the dot and in its near vicinity, only. The accurate positioning of the dots on pre-patterned substrates enables the utilization of these substrates for further device processing. The crucial issue is to integrate the active area on top of the dot, which requires an overlay of ± 10 nm, which has to be assured over the whole process. In this paper we investigate the intrinsic overlay of a Vistec EBPG 5000^plus e-beam system using etched holes in silicon as markers. It was found, that the required overlay accuracy can be obtained, when the definition of the marker sites is adapted to the following process, already. The overlay is not affected by device processing, as long as the markers are affected symmetrically.     

Scaling considerations for sub-90 nm split-gate flash

A systematic methodology is presented to scale split-gate (SG) flash memory cells in the sub-90 nm regime within the presently known scaling constraints of flash memory. The numerical device simulation results show that the high performance sub-90 nm NOR-type SG cells can be achieved by a suitable channel and source-drain engineering. An asymmetric channel doping profile along with ultra-shallow source-drain junctions was used to achieve the target drain programming voltage (V_sp) for an efficient cell programming while keeping the cell breakdown voltage, BV > V_sp, with tolerable leakage currents. The study shows that with properly optimised technology parameters, 65 nm SG-NOR flash memory can be achieved with an adequate cell read current, a tolerable programmed cell leakage current at the read condition and efficient write and erase times.     

Sub-100 nanometer channel length Ge/Si nanowire transistors with potential for 2 THz switching speed

Ge/Si core/shell nanowires (NWs) are attractive and flexible building blocks for nanoelectronics ranging from field-effect transistors (FETs) to low-temperature quantum devices. Here we report the first studies of the size-dependent performance limits of Ge/Si NWFETs in the sub-100 nm channel length regime. Metallic nanoscale electrical contacts were made and used to define sub-100 nm Ge/Si channels by controlled solid-state conversion of Ge/Si NWs to NiSixGe y alloys. Electrical transport measurements and modeling studies demonstrate that the nanoscale metallic contacts overcome deleterious short-channel effects present in lithographically defined sub-100 nm channels. Data acquired on 70 and 40 nm channel length Ge/Si NWFETs with a drain-source bias of 0.5 V yield transconductance values of 78 and 91 microS, respectively, and maximum on-currents of 121 and 152 microA. The scaled transconductance and on-current values for a gate and bias voltage window of 0.5 V were 6.2 mS/microm and 2.1 mA/microm, respectively, for the 40 nm device and exceed the best reported values for planar Si and NW p-type FETs. In addition, analysis of the intrinsic switching delay shows that terahertz intrinsic operation speed is possible when channel length is reduced to 70 nm and that an intrinsic delay of 0.5 ps is achievable in our 40 nm device. Comparison of the experimental data with simulations based on a semiclassical, ballistic transport model suggests that these sub-100 nm Ge/Si NWFETs with integrated high-kappa gate dielectric operate near the ballistic limit.     

Optimization of extrinsic source/drain resistance in ultrathin body double-gate FETs

Extrinsic resistance due to contacts and nonabrupt lateral extension doping profile can become a performance-limiter in ultrathin body double-gate FETs (DGFET). In this paper, two-dimensional device simulations are used to study and optimize the extrinsic resistance in a sub-20 nm gate length DGFET. For a given lateral doping gradient, the extension doping needs to be offset from the gate edge by an amount called the underlap. The current drive, and hence transistor performance, is maximized when the underlap is chosen in such a way as to balance the impact of nonabrupt doping on the short channel effects and series resistance. This optimization depends upon the maximum allowed off-state subthreshold leakage current and the electrostatic integrity of the device structure.     

Sub-20-nm alignment in nanoimprint lithography using Moiré fringe

Accurate multi-level overlay capability for nanoimprint lithography (NIL) is essential to integrated circuit manufacturing and other multilayer imprint applications. Using the "beat" grating image (Moiré fringe) generated by overlaying two sets of gratings that have slightly different periods, we obtained an alignment signal with a sensitivity better than 10 nm in nanoimprint lithography. The alignment signal is, as expected, independent of the size of the gap between the wafer and the imprint mold. We achieved a single-point overlay accuracy (error distribution) of sub-20 nm between the first and second imprinted layers by using two sets of Moiré fringes. With higher precision nanopositioning stages, better single-point alignment accuracy is expected. Furthermore, we achieved sub-150 nm alignment over an area of 1 sq in and sub-250 nm over the entire area of a 4 in wafer using simple low-resolution stages without temperature control or wafer-mold mismatch compensation. With better stages, precision temperature control, and wafer-mold mismatch compensation, we believe that much higher overlay alignment accuracy over large areas (either in a 1 sq in die or a full wafer) is feasible.     

Two-dimensional dopant profiling by electrostatic force microscopy using carbon nanotube modified cantilevers

A two-dimensional (2D) dopant profiling technique is demonstrated in this work. We apply a unique cantilever probe in electrostatic force microscopy (EFM) modified by the attachment of a multiwalled carbon nanotube (MWNT). Furthermore, the tip apex of the MWNT was trimmed to the sharpness of a single-walled carbon nanotube (SWNT). This ultra-sharp MWNT tip helps us to resolve dopant features to within 10?nm in air, which approaches the resolution achieved by ultra-high vacuum scanning tunnelling microscopy (UHV STM). In this study, the CNT-probed EFM is used to profile 2D buried dopant distribution under a nano-scale device structure and shows the feasibility of device characterization for sub-45?nm complementary metal-oxide-semiconductor (CMOS) field-effect transistors.     

Large-scale homogeneously distributed Ag-NPs with sub-10 nm gaps assembled on a two-layered honeycomb-like TiO(2) film as sensitive and reproducible SERS substrates

We present a surface-enhanced Raman scattering (SERS) substrate featured by large-scale homogeneously distributed Ag nanoparticles (Ag-NPs) with sub-10?nm gaps assembled on a two-layered honeycomb-like TiO(2) film. The two-layered honeycomb-like TiO(2) film was achieved by a two-step anodization of pure Ti foil, with its upper layer consisting of hexagonally arranged shallow nano-bowls of 160?nm in diameter, and the lower layer consisting of arrays of about fifty vertically aligned sub-20?nm diameter nanopores. The shallow nano-bowls in the upper layer divide the whole TiO(2) film into regularly arranged arrays of uniform hexagonal nano-cells, leading to a similar distribution pattern for the ion-sputtered Ag-NPs in each nano-cell. The lower layer with sub-20?nm diameter nanopores prevents the aggregation of the sputtered Ag-NPs, so that the Ag-NPs can get much closer with gaps in the sub-10?nm range. Therefore, large-scale high-density and quasi-ordered sub-10?nm gaps between the adjacent Ag-NPs were achieved, which ensures homogeneously distributed 'hot spots' over a large area for the SERS effect. Moreover, the honeycomb-like structure can also facilitate the capture of target analyte molecules. As expected, the SERS substrate exhibits an excellent SERS effect with high sensitivity and reproducibility. As an example, the SERS substrate was utilized to detect polychlorinated biphenyls (PCBs, a kind of persistent organic pollutants as global environmental hazard) such as 3,3',4,4'-pentachlorobiphenyl (PCB-77) with concentrations down to 10(-9)?M. Therefore the large-scale Ag-NPs with sub-10?nm gaps assembled on the two-layered honeycomb-like TiO (2) film have potentials in SERS-based rapid trace detection of PCBs.     

Doping-free fabrication of carbon nanotube thin-film diodes and their photovoltaic characteristics

Random networks of single-walled carbon nanotubes (SWCNTs) were have been grown by chemical vapor deposition on silicon wafers and used for fabricating field-effect transistors (FETs) using symmetric Pd contacts and diodes using asymmetrical Pd and Sc contacts. For a short channel FET or diode with a channel length of about 1 μm or less, the device works in the direct transport regime, while for a longer channel device the transport mechanism changes to percolation. Detailed electronic and photovoltaic (PV) characterizations of these carbon nanotube (CNT) thin-film devices was carried out. While as-fabricated FETs exhibited typical p-type transfer characteristics, with a large current ON/OFF ratio of more than 10⁴ when metallic CNTs were removed via a controlled breakdown, it was found that the threshold voltage for the devices was typically very large, of the order of about 10 V. This situation was greatly improved when the device was coated with a passivation layer of 12 nm HfO₂, which effectively moved the threshold voltages of both FET and diode back to center around zero or turned these device to their OFF states when no bias was applied on the gate. PV measurements were then made on the short channel diodes under infrared laser illumination. It was shown that under an illumination power density of 1.5 kW/cm², the device resulted in an open circuit voltage V _OC = 0.21 V and a short circuit current I _SC = 3.74 nA. Furthermore, we compared PV characteristics of CNT film diodes with different channel lengths, and found that the power transform efficiency decreased significantly when the device changed from the direct transport to the percolation regime.     

Formation and photoluminescence of Si nanocrystals in controlled multilayer structure comprising of Si-rich nitride and ultrathin silicon nitride barrier layers

The effect of ultrathin silicon nitride (Si₃N₄) barrier layers on the formation and photoluminescence (PL) of Si nanocrystals (NCs) in Si-rich nitride (SRN)/Si₃N₄ multilayer structure was investigated. The layered structures composed of alternating layers of SRN and Si₃N₄ were prepared using magnetron sputtering followed by a different high temperature annealing. The formation of uniformly sized Si NCs was confirmed by the transmission electron microscopy and X-ray diffraction measurements. In particular, the 1 nm thick Si₃N₄ barrier layers was found to be sufficient in restraining the growth of Si NCs within the SRN layers upon high annealing processes. Moreover, X-ray photoelectron spectroscopy spectra shown that films subjected to post-anneal processes were not oxidized during the annealing. X-ray reflection measurements revealed that high annealing process induced low variation in the multilayer structure where the 1 nm Si₃N₄ layers act as good diffusion barriers to inhibit inter-diffusion between SRN layers. The PL emission observed was shown to be originated from the quantum confinement of Si NCs in the SRN. Furthermore, the blue shift of PL peaks accompanied by improved PL intensity after annealing process could be attributed to the effect of improved crystallization as well as nitride passivation in the films. Such multilayer structure should be advantageous for photovoltaic applications as the ultrathin barrier layer allow better electrical conductivity while still able to confine the growth of desired Si NC size for bandgap engineering.     

Helium ion beam milling to create a nano-structured domain wall magnetoresistance spin valve

We have fabricated and measured single domain wall magnetoresistance devices with sub-20?nm gap widths using a novel combination of electron beam lithography and helium ion beam milling. The measurement wires and external profile of the spin valve are fabricated by electron beam lithography and lift-off. The critical bridge structure is created using helium ion beam milling, enabling the formation of a thinner gap (and so a narrower domain wall) than that which is possible with electron beam techniques alone. Four-point probe resistance measurements and scanning electron microscopy are used to characterize the milled structures and optimize the He ion dose. Successful operation of the device as a spin valve is demonstrated, with a 0.2% resistance change as the external magnetic field is cycled. The helium ion beam milling efficiency as extracted from electrical resistance measurements is 0.044?atoms/ion, about half the theoretical value. The gap in the device is limited to a maximum of 20?nm with this technique due to sub-surface swelling caused by injected ions which can induce catastrophic failure in the device. The fine patterning capabilities of the helium ion microscope milling technique indicate that sub-5?nm constriction widths could be possible.     

A Self‐Powered Sensor Mimicking Slow‐ and Fast‐Adapting Cutaneous Mechanoreceptors

Highly efficient human skin systems transmit fast adaptive (FA) and slow adaptive (SA) pulses selectively or consolidatively to the brain for a variety of external stimuli. The integrated analysis of these signals determines how humans perceive external physical stimuli. Here, a self‐powered mechanoreceptor sensor based on an artificial ion‐channel system combined with a piezoelectric film is presented, which can simultaneously implement FA and SA pulses like human skin. This device detects stimuli with high sensitivity and broad frequency band without external power. For the feasibility study, various stimuli are measured or detected. Vital signs such as the heart rate and ballistocardiogram can be measured simultaneously in real time. Also, a variety of stimuli such as the mechanical stress, surface roughness, and contact by a moving object can be distinguished and detected. This opens new scientific fields to realize the somatic cutaneous sensor of the real skin. Moreover, this new sensing scheme inspired by natural sensing structures is able to mimic the five senses of living creatures.     

Polymer light-emitting devices based on plasma-polymerized benzene and plasma-polymerized naphthalene

Polymer light-emitting devices (PLED) were fabricated utilizing plasma-polymerized benzene (PPB) and plasma-polymerized naphthalene (PPN) as an electroluminescent (EL) emitting layer. The plasma polymerization is well suited for forming the transparent, sturdy thin film for EL polymer layers. For the ITO/PPB/Al and ITO/PPN/Al devices, the turn-on voltage of the device was at 12V and 6V, respectively. The luminance of the PPB device reached 6 cdm ^-2 at 10 V, whereas the PPN device reached 11 cd m ^-2 at 14 V. The external quantum efficency was 0.0035% for the PPB device and 0.0056% for the PPN device. The dense crosslinked structure formed by the plasma polymerization makes the EL device relatively stable during operation. © 2001 Kluwer Academic Publishers     

Printing of sub-20 nm wide graphene ribbon arrays using nanoimprinted graphite stamps and electrostatic force assisted bonding

Nano-graphene ribbons are promising in many electronic applications, as their bandgaps can be opened by reducing the widths, e.g. below 20 nm. However, a high-throughput method to pattern large-area nano-graphene features is still not available. Here we report a fabrication method of sub-20 nm ribbons on graphite stamps by nanoimprint lithography and a transfer-printing of the graphene ribbons to a Si wafer using electrostatic force assisted bonding. These methods provide a path for fast and high-throughput nano-graphene device production.     

Fabrication of periodic metal nanowires with microscale mold by nanoimprint lithography

In this paper, a simple method is demonstrated for fabricating periodic metal nanowires based on the unconventional nanoimprint lithography (NIL) technique. Using this method, sub-100 nm metal nanowires with the rectangular cross-section are fabricated with microscale stamp. Furthermore, the metal nanowires with different widths and heights can be generated by adjusting the imprinting parameters with the same stamp. The metal nanowires prepared with this method can be used for chemical sensing, such as ammonia sensing, and it may have applications in optical signal processing.