Sharp Turn-on Research Articles

Scalable on-chip multiplexing of silicon single and double quantum dots

Owing to the maturity of complementary metal oxide semiconductor (CMOS) microelectronics, qubits realized with spins in silicon quantum dots (QDs) are considered among the most promising technologies for building scalable quantum computers. For this goal, ultra-low-power on-chip cryogenic CMOS (cryo-CMOS) electronics for control, read-out, and interfacing of the qubits is an important milestone. We report on-chip interfacing of tunable electron and hole QDs by a 64-channel cryo-CMOS multiplexer with less-than-detectable static power dissipation. We analyze charge noise and measure state-of-the-art addition energies and gate lever arm parameters in the QDs. We correlate low noise in QDs and sharp turn-on characteristics in cryogenic transistors, both fabricated with the same gate stack. Finally, we demonstrate that our hybrid quantum-CMOS technology provides a route to scalable interfacing of a large number of QD devices, enabling, for example, variability analysis and QD qubit geometry optimization, which are prerequisites for building large-scale silicon-based quantum computers.

New dual-responsive fluorescent sensor for hypochlorite and cyanide sensing and its imaging application in live cells and zebrafish

Excessive levels of cyanide (CN−) and hypochlorite (ClO−) anions are the significant threats to the human health and the environment. Thus, great efforts have been to design and synthesize molecular sensors for the simple, instantaneous and efficient detecting environmentally and biologically important anions. Currently, developing a single molecular sensor for multi-analyte sensing is still a challenging task. In our present work, we developed a new molecular sensor (3TM) based on oligothiophene and Meldrum's acid units for detecting cyanide and hypochlorite anions in biological, environmental and food samples. The detecting ability of 3TM has been examined to various testing substances containing amino acids, reactive oxygen species, cations and anions, showing its high selectivity, excellent sensitivity, short response time (ClO−: 30 s, CN−: 100 s), and broad pH working range (4–10). The detection limits were calculated as 4.2 nM for ClO− in DMSO/H2O (1/8, v/v) solution and 6.5 nM for CN− in DMSO/H2O (1/99, v/v) solution. Sensor 3TM displayed sharp turn-on fluorescence increasement (555 nm, 435 nm) and sensitive fluorescence color changes caused by CN−/ClO−, which is ascribed to the nucleophilic addition and oxidation of ethylenic linkage by cyanide and hypochlorite, respectively. Moreover, sensor 3TM was applied for hypochlorite and cyanide detecting in real-world water, food samples and bio-imaging in live cells and zebrafish. To our knowledge, the developed 3TM sensor is the seventh single-molecular sensor for simultaneous and discriminative detecting hypochlorite and cyanide in food, biological and aqueous environments using two distinct sensing modes.

A General Twisted Intramolecular Charge Transfer Triggering Strategy by Protonation for Zero-Background Fluorescent Turn-On Sensing

The exploration of organic fluorescent sensing materials and mechanisms is of great significance, especially for the deep understanding of twisted intramolecular charge transfer (TICT). Here, the electron-donating ability of a chemically protonated amino group and the corresponding excitation primarily ensure the occurrence of excited-state intramolecular proton transfer. Due to the hybridization of the amino group from sp3 to sp2, the steric hindrance effect and conjugative effect together boost the rotation efficiency of the TICT process and the complete elimination of the background fluorescent signal. Furthermore, a sharp turn-on fluorescent detection of trace nitrite particulate with a diameter of 0.44 μm was realized. In addition, this protonation-induced change in the amino group configuration was verified through around nine categories of compounds. We expect this modulation of the photochemical activity path of the TICT process would greatly facilitate the exploration of novel fluorescent sensing mechanisms.

Remarkably High-Performance Nanosheet GeSn Thin-Film Transistor.

High-performance p-type thin-film transistors (pTFTs) are crucial for realizing low-power display-on-panel and monolithic three-dimensional integrated circuits. Unfortunately, it is difficult to achieve a high hole mobility of greater than 10 cm2/V·s, even for SnO TFTs with a unique single-hole band and a small hole effective mass. In this paper, we demonstrate a high-performance GeSn pTFT with a high field-effect hole mobility (μFE), of 41.8 cm2/V·s; a sharp turn-on subthreshold slope (SS), of 311 mV/dec, for low-voltage operation; and a large on-current/off-current (ION/IOFF) value, of 8.9 × 106. This remarkably high ION/IOFF is achieved using an ultra-thin nanosheet GeSn, with a thickness of only 7 nm. Although an even higher hole mobility (103.8 cm2/V·s) was obtained with a thicker GeSn channel, the IOFF increased rapidly and the poor ION/IOFF (75) was unsuitable for transistor applications. The high mobility is due to the small hole effective mass of GeSn, which is supported by first-principles electronic structure calculations.

Sensing of aluminum and cyanide ions utilizing a novel bis-phenol a based fluorogenic probe: Applications in test stripts

Excessive levels of some cations and anions such as aluminum and cyanine ions are well known ions as the most important threats thanks to their high toxicity to environment and human health. In the present study, a novel and selective fluorogenic probe BAFH possessing bisphenol A and 2-furoic hydrazide units for the binding has been designed and prepared to recognize Al3+ and CN− selectively. The probe BAFH undergoes sharp turn-on emission increment caused by Al3+ and CN− over other competitive cations and anions. BAFH could effectively and selectively recognize aluminum or cyanide with a low detection limit value of 2.66 and 4.81 nm, respectively. The selectivity and sensitivity behavior of BAFH was obtained in the presence of competitive anions and cations and allow to it a superb property for the recognition of Al3+ and CN− in acetonitrile-HEPES (8:2, v/v) media. Moreover, the possible employment of BAFH was effectively tested in test kits.

(Invited) Monolithic Integration of Zinc Tin Oxide Electronics

Oxide semiconductors’ unique properties – a wide bandgap, reasonably high electron mobility, and ease of bulk and thin film preparation – make them prime material candidates for a variety of electronic devices. In this talk, I will describe my group’s recent demonstration of amorphous zinc tin oxide (a-ZTO) electronic devices for thin film monolithic integration of comparatively high voltage (2 to 100 V) power electronics on top of low voltage (VDD ~ 1.2V) state-of-the-art silicon CMOS. We use an in-air solution process to synthesize a-ZTO semiconductor thin films. The resulting bottom-gate, top-contact transistors have field effect mobility of 8.3 cm2V-1s-1 and enhancement-mode behavior with turn-on near zero volts. By controlling ink dilution, we form homogeneous, amorphous channel layers less than 10 nm thick. When passivated with ozone-based atomic layer deposition of Al2O3 to stabilize the exposed top surface of the active layer, the transistors have excellent bias stress stability and sharp sub-threshold turn-on [1,2]. Next, we successfully integrated our thin film a-ZTO transistors directly on top of silicon finFET CMOS in the back end of line. The ZTO device fabrication process is fully compatible with finFET CMOS: after ZTO transistor formation, both the bottom silicon transistors and top a-ZTO transistors function well, with no degradation in performance. To expand the range of devices available for ZTO circuit design, we then developed several other device technologies. Using the Gibbs free energy of oxide formation and ionic radii of the bottom metal thin films as selection criteria, we chose metal contact layers and device structure to form multiple types of components – MISFETs, MESFETs, Schottky diodes, and resistive memory devices [3–5] – using one integrated fabrication process. With these devices, we demonstrate three applications. First, we make full-wave rectifiers that can harvest wireless power from commercial 13.56 MHz RFID signals and use the resulting d.c. voltage to switch underlying low voltage silicon finFETs. Second, we make logic inverters with low switching voltage window and single-transistor amplifiers with high gain by combining a depletion-mode MESFET device as a load and enhancement-mode MISFET devices as the drive transistor. Third, by incorporating a gate-drain offset into the MISFET design, we increase the TFT blocking voltage to above 100 V, enabling future 3-D monolithic integration of high voltage / low voltage interface power electronic circuits on top of silicon CMOS ICs [6].Thanks to G. A. Torres Sevilla and M. M. Hussain for providing silicon CMOS, N. Dasgupta and C. Huber for depositing alumina with ozone, and W. Hu, J. Li and J. Miller for help with TFT fabrication. This work was supported by SPAWAR through DARPA Young Faculty Award N66001-14-1-4046. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of DARPA or SPAWAR. Y.S. was supported in part by the Kwanjeong Educational Foundation. Portions of the work were performed in the Lurie Nanofabrication Facility, which is supported by the University of Michigan’s College of Engineering.[1] C. R. Allemang, R. L. Peterson, IEEE Electron Device Lett. 2019, 40, 1120; [2] Y. Son, A. Liao, R. L. Peterson, J Mater Chem C 2017, 5, 8071; [3] Y. Son, R. L. Peterson, in 2017 75th Annu. Device Res. Conf. DRC, 2017, pp. 1–2; [4] Y. Son, R. L. Peterson, Adv. Funct. Mater. 2019, 29, 1806002; [5] Y. Son, B. Frost, Y. Zhao, R. L. Peterson, Nat. Electron. 2019, 2, 540; [6] C. Allemang, R. L. Peterson, in 2017 75th Annu. Device Res. Conf. DRC, IEEE, South Bend, IN, 2017, pp. 1–2.

Solution-processed flexible metal-oxide thin-film transistors operating beyond 20 MHz

Complementary metal-oxide-semiconductor, an elementary building block, allows for a high degree of implementation of logic circuits with relatively low power consumption and low manufacturing cost, which plays a vital role not only in current Si electronics, but also in printed flexible devices. To meet the looming challenges of the Internet of Things, p-channel thin-film transistors (TFTs) with an excellent mobility and processability have been increasingly developed using organic semiconductors. However, owing to the inherent electron-donating nature of organic compounds, the high performance of n-channel organic TFTs has yet to be demonstrated. Here, in this paper, we developed state-of-the-art solution-processed indium-zinc-oxide (IZO) TFTs with high electron mobility, sharp turn-on characteristics at 0 V, and excellent atmospheric stability and compatibility with wet patterning processes. With the damage-free lithography process in conjunction with the ultimate optimization of entire device processes, IZO-based TFT arrays were successfully fabricated via a solution process on flexible polyimide substrates. A cutoff frequency of 23 MHz in air was achieved, which is almost twice as fast as the frequency used in a near-field communication band. Furthermore, the as-fabricated IZO-based TFTs even function well under bending stress. Therefore, the current concept and technique is expected to open up opportunities to develop practical flexible devices with high-speed operation.

Red and blue emitting fluorescent probe for cyanide and hypochlorite ions: Biological sensing and environmental analysis

Excessive levels of hypochlorite and cyanide ions are considered as the major threats towards human health and environment. Therefore, many researchers make considerable effort to develop small molecules for the quick, accurate and easy detection of biologically and environmentally important anions. Moreover, design of multiple analyte sensing sensors is still challenging issue due to broad application area. In the present study, we introduce a novel chemosensor (P) based on benzothiazole and diaminomaleonitrile units for the detection hypochlorite and cyanide ions in biological and environmental samples. The detection ability of P was examined towards a pool of analyte containing anions, cations and reactive oxygen species. P undergoes sharp turn-on fluorescence enhancement induced by hypochlorite or cyanide over other anions. The fluorescence response is attributed to oxidation of imine bond by hypochlorite or deprotonation of –NH2 and –OH functions by cyanide. The selectivity and sensitivity data demonstrated by P over other anions renders it an excellent candidate for hypochlorite and cyanide detection in biological and aqueous environments. Moreover, this is the first study that single probe has an ability of detecting both hypochlorite and cyanide anions through two distinct sensing modes.

Naphthalimide-amino acid conjugates chemosensors for Hg2+ detection: Based on chelation mediated emission enhancement in aqueous solution

1,8–Naphthalimide-Amino acid conjugates (L4 and L5) were designed, synthesized via straight forward reaction for Hg+2 ion sensing. These chemosensors were found displaying aggregation-induced emission (AIE) property along with an increased quantum yield upon changing the medium from methanol to CH3OH:H2O (1:99, v/v). They exhibited a quick response, splendid selectivity and sensitivity toward Hg2+ ion over other interfering tested metal ions through sharp turn-on fluorescence via chelation mediated aggregation-induced emission in CH3OH /H2O (1:99, v/v) medium. Job’s plot revealed the formation of 2:1 ligand to metal stoichiometry and L4 and L5 can detect Hg2+ ion as low as 22 nM and 5.6 nM respectively. Interestingly, the fluorescence reversibility study showed good result by adding Hg2+ and KI salts sequentially.

First-level muon track trigger for future hadron collider experiments

Abstract Single muon triggers are crucial for the physics programmes as hadron collider experiments. To be sensitive to electroweak processes, single muon triggers with transverse momentum thresholds down to 20 GeV and dimuon triggers with even lower thresholds are required. In order to keep the rates of these triggers at an acceptable level these triggers have to be highly selective, i.e. they must have small accidental trigger rates and sharp trigger turn-on curves. The muon systems of the LHC experiments and experiments at future colliders like FCC-hh will use two muon chamber systems for the muon trigger, fast trigger chambers like RPCs with coarse spatial resolution and much slower precision chambers like drift–tube chambers with high spatial resolution. The data of the trigger chambers are used to identify the bunch crossing in which the muon was created and for a rough momentum measurement while the precise measurements of the muon trajectory by the precision chambers are ideal for an accurate muon momentum measurement. A concept for the muon trigger of the baseline detector for the FCC-hh which exploits the precision measurements of drift–tube chambers is presented including the description and the test of a compact muon track reconstruction algorithm.

Hardware demonstrator of a compact first-level muon track trigger for future hadron collider experiments

Single muon triggers are crucial for the physics programmes at hadron collider experiments. To be sensitive to electroweak processes, single muon triggers with transverse momentum thresholds down to 20 GeV and dimuon triggers with even lower thresholds are required. In order to keep the rates of these triggers at an acceptable level these triggers have to be highly selective, i.e. they must have small accidental trigger rates and sharp trigger turn-on curves. The muon systems of the LHC experiments and experiments at future colliders like FCC-hh will use two muon chamber systems for the muon trigger, fast trigger chambers like RPCs with coarse spatial resolution and much slower precision chambers like drift-tube chambers with high spatial resolution. The data of the trigger chambers are used to identify the bunch crossing in which the muon was created and for a rough momentum measurement while the precise measurements of the muon trajectory by the precision chambers are ideal for an accurate muon momentum measurement. A compact muon track finding algorithm is presented, where muon track candidates are reconstructed using a binning algorithm based on a 1D Hough Transform. The algorithm has been designed and implemented on a System-On-Chip device. A hardware demonstration using Xilinx Evaluation boards ZC706 has been set-up to prove the concept. The system has demonstrated the feasibility to reconstruct muon tracks with a good angular resolution, whilst satisfying latency constraints. The demonstrated track-reconstruction system, the chosen architecture, the achievements to date and future options for such a system will be discussed.

Core-shell p-i-n GaN nanowire LEDs by N-polar selective area growth.

GaN nanowire LEDs with radial p-i-n junctions were grown by molecular beam epitaxy using N-polar selective area growth on Si(111) substrates. The N-polar selective area growth process facilitated the growth of isolated and high-aspect-ratio n-type NW cores that were not subject to self-shadowing effects during the subsequent growth of a conformal low-temperature Mg:GaN shell. LED devices were fabricated from single-NW and multiple-NW arrays in their as-grown configuration by contacting the n-type core through an underlying conductive GaN layer and the p-type NW shell via a metallization layer. The NW LEDs exhibited rectifying I-V characteristics with a sharp turn-on voltage near the GaN bandgap and low reverse bias leakage current. Under forward bias, the NW LEDs produced electroluminescence with a peak emission wavelength near 380 nm and exhibited a small spectral blueshift with increasing current injection, both of which are consistent with electron recombination in the p-type shell layer through donor-acceptor-pair recombination. These core-shell NW devices demonstrate N-polar selective area growth as an effective technique for producing on-chip nanoscale light sources.

Diode Characteristics of a Super-Steep Subthreshold Slope PN-Body Tied SOI-FET for Energy Harvesting Applications

In this paper, the diode characteristics of our newly proposed super-steep subthreshold slope “PN-body tied (PNBT) silicon-on-insulator field-effect transistor” are presented, and compared with conventional diodes. We report that the device possesses super-steep characteristics, low leakage current, and sharp turn-on characteristics, even in the ultralow voltage range (50 mV). These indicate that the PNBT diode can potentially be used in high-efficiency rectification for energy harvesting, particularly in situations where there is ultralow input power. In addition, the hysteresis characteristics and the slight shift of the voltage at zero current are confirmed as specific characteristics of PNBT diodes.

TiO2 Nanowires/Poly(Methyl Methacrylate) Based Hybrid Photodetector: Improved Light Detection.

Hybrid photodetector with a maximum external quantum efficiency of ~3.08% in the UV region at 370 nm, was fabricated by spin-coated poly(methyl methacrylate) (PMMA) polymer onto glancing angle deposited (GLAD) vertically aligned TiO2 nanowire (NW) arrays. The TiO2 NWs/PMMA detector shows excellent rectification and constant 1.3 times photo-responsivity in the reverse bias condition from -1 V to -10 V. The photodiode possesses a low ideality factor of 5.1 as compared to bared TiO2 NWs device of 7.1. The hybrid device produces sharp turn-on of -0.8 s and turn-off transient of -0.9 s respectively.

Topological Insulator Bi2Se3 Nanowire Field Effect Transistors

Topological insulator is characterized as a new class of materials which have an insulating band gap in the bulk and gapless surface state which is protected by its intrinsic time-reversal symmetry. Here, we report high-performance topological insulator nanowire field effect transistors (FETs) with sharp turn-on, clear cutoff current, large On/Off current ratio (~ 108) and well-saturated, strong inversion-mode output current-voltage characteristics. The metallic electron transport at surface, with effective mobility of 200 cm2V-1s-1 ~ 1000 cm2V-1s-1, and bulk conduction, with activation energy close to band gap of bulk Bi2Se3 can be effectively separated and tuned by gated field effect. We also report the first experimental observation of anomalous Aharonov-Bohm oscillation in Bi2Se3 nanowire FET under strong surface disorder. The magnetotransport properties demonstrated here of topological insulator nanostructure provide effective approaches of surface states modulations, and can enable more spintronics device applications and sensing applications.

Topological Insulator Bi2Se3 Nanowire High Performance Field-Effect Transistors

Topological insulators are unique electronic materials with insulating interiors and robust metallic surfaces. Device applications exploiting their remarkable properties have so far been hampered by the difficulty to electrically tune the Fermi levels of both bulk and thin film samples. Here we show experimentally that single-crystal nanowires of the topological insulator Bi2Se3 can be used as the conduction channel in high-performance field effect transistor (FET), a basic circuit building block. Its current-voltage characteristics are superior to many of those reported for semiconductor nanowire transistors, including sharp turn-on, nearly zero cutoff current, very large On/Off current ratio, and well-saturated output current. The metallic electron transport at the surface with good FET effective mobility can be effectively separated from the conduction of bulk Bi2Se3 and adjusted by field effect at a small gate voltage. This opens up a suite of potential applications in nanoelectronics and spintronics.

P-Cu2O-shell/n-TiO2-nanowire-core heterostucture photodiodes

This study reports the deposition of cuprous oxide [Cu2O] onto titanium dioxide [TiO2] nanowires [NWs] prepared on TiO2/glass templates. The average length and average diameter of these thermally oxidized and evaporated TiO2 NWs are 0.1 to 0.4 μm and 30 to 100 nm, respectively. The deposited Cu2O fills gaps between the TiO2 NWs with good step coverage to form nanoshells surrounding the TiO2 cores. The p-Cu2O/n-TiO2 NW heterostructure exhibits a rectifying behavior with a sharp turn-on at approximately 0.9 V. Furthermore, the fabricated p-Cu2O-shell/n-TiO2-nanowire-core photodiodes exhibit reasonably large photocurrent-to-dark-current contrast ratios and fast responses.

Charge transport in high-performance ink-jet printed single-droplet organic transistors based on a silylethynyl substituted pentacene/insulating polymer blend

We present a systematic study of the influence of material composition and ink-jet processing conditions on the charge transport in bottom-gate field-effect transistors based on blends of 6,13-bis(triisopropyl-silylethynyl) pentacene (TIPS-PEN) and polystyrene. After careful process optimizations of blending ratio and printing temperature we routinely can make transistors with an average mobility of 1 cm 2/Vs (maximum value 1.5 cm 2/Vs), on/off ratio exceeding 10 7, and sharp turn-on in current (sub-threshold slopes approaching 60 mV/decade). These characteristics are superior to the TIPS-PEN only transistors. Using channel scaling measurements and scanning Kelvin probe microscopy, the sharp turn-on in current in the blends is attributed to a contact resistance that originates from a thin insulating layer between the injecting contacts and the semiconductor channel.

Energy efficient microcavity lasers with 20 and 40 Gb/s data transmission

Microcavity lasers (μCLs), reduced-size (≲3 μm aperture) vertical cavity surface-emitting lasers (VCSELs) defined by the buried-oxide process for current and field confinement (thus wide mode spacing), are demonstrated with low threshold current, sharp turn-on L-I characteristics, and wide bandwidth operation. Due to the enhanced spontaneous recombination rate at reduced mode and improved photon density, μCLs exhibit lower charge-field resonance peaks at a modulation bandwidth f−3 dB=18.7 GHz, thus permitting open-“eye” operation at 20 and 40 Gb/s data rates (I≲3 mA). The energy efficiency for 20 Gb/s data transmission is measured to be 4.84 Gb/s/mW, which is eight times better than 7 μm aperture VCSELs.

Tellurium doping of InGaP for tunnel junction applications in triple junction solar cells

Tellurium doped InGaP is an ideal material for the n side of a tunnel junction for triple junction solar cell structures grown by MOCVD. In this paper, we discuss the growth process for abrupt turn-on and turn-off of tellurium in InGaP when InGaP must be highly doped and uniformly doped with tellurium to provide for epitaxial films suitable for tunnel junctions. Results show that tellurium pre-doping of the layer before InGaP growth provides for a sharp turn-on and that using a growth pause at elevated growth temperatures after InGaP provides for a sharp turn-off in the doping profile. Results from a series of experiments in which partial pressure of phosphine and growth temperature were varied show that doping levels of >1×10 19 cm −3 can be achieved uniformly over 4 in. diameter germanium wafers by lowering growth temperature and V/III ratio. Results also showed that high tellurium doping levels strain InGaP and adjustment of indium mole fraction in InGaP is required to produce smooth epitaxial layers. These MOCVD growth processes can be incorporated in the growth of tunnel junction layers used in the production of triple junction solar cells.