Aixia Lu

Low-voltage electric-double-layer paper transistors gated by microporous SiO2 processed at room temperature

Battery drivable low-voltage SnO2-based paper thin-film transistors with a near-zero threshold voltage (Vth=0.06 V) gated by microporous SiO2 dielectric with electric-double-layer (EDL) effect are fabricated at room temperature. The operating voltage is found to be as low as 1.5 V due to the huge gate specific capacitance (1.34 μF/cm2 at 40 Hz) related to EDL formation. The subthreshold gate voltage swing and current on/off ratio is found to be 82 mV/decade and 2.0×105, respectively. The electron field-effect mobility is estimated to be 47.3 cm2/V s based on the measured gate specific capacitance at 40 Hz.

One-Shadow-Mask Self-Assembled Ultralow-Voltage Coplanar Homojunction Thin-Film Transistors

A self-assembling diffraction method is developed for low-voltage coplanar homojunction thin-film transistor (TFT) fabrication. In this one-shadow-mask process, a channel layer can be simultaneously self-assembled between indium-tin-oxide (ITO) source/drain electrodes during magnetron sputtering deposition. When a microporous SiO2-based solid electrolyte is used as the gate dielectric, full-depletion-mode ITO TFTs show an ultralow operation voltage of 1.5 V due to the large specific capacitance (4.44 μF/cm2). A small subthreshold swing of 0.12 V/decade and a large on/off ratio of 106 are obtained. Our results demonstrate that such a simple one-mask self-assembling method is promising for low-cost TFT fabrication.

Microporous SiO2 with huge electric-double-layer capacitance for low-voltage indium tin oxide thin-film transistors

Electric-double-layer (EDL) effect is observed in microporous SiO2 dielectric films deposited at room temperature by plasma-enhanced chemical vapor deposition method. Indium tin oxide thin-film transistors gated by such microporous SiO2 gate dielectric are fabricated at room temperature, and a low operating voltage of 1.5 V is obtained due to the huge EDL specific capacitance (2.14 μF/cm2). The field-effect electron mobility is estimated to be 118 cm2 V−1 s−1. Current on/off ratio and subthreshold gate voltage swing are estimated to be 5×106 and 92 mV/decade, respectively. Room-temperature deposited microporous SiO2 dielectric is promising for low-power field-effect transistors on temperature sensitive substrates.

Ultralow-voltage transparent electric-double-layer thin-film transistors processed at room-temperature

Electric-double-layer effect is observed in mesoporous SiO2 films deposited by plasma-enhanced chemical vapor deposition at room temperature. Room-temperature processed transparent InGaZnO4 thin film transistors (TFTs) gated with such mesoporous SiO2 dielectric show an ultralow operating voltage of 1.0 V due to the large electric-double-layer capacitance. The InGaZnO4 TFTs exhibit a good performance with a high field-effect mobility of 28.5 cm2/V s, a low subthreshold swing of 110 mV/decade, and a large on-off ratio of 1.1×106, respectively. Such ultralow-voltage devices are very promising for low-power transparent macroelectronics on temperature-sensitive substrates.

Low-voltage transparent electric-double-layer ZnO-based thin-film transistors for portable transparent electronics

Room-temperature deposited 8.0 μm-thick mesoporous SiO2 dielectric shows a huge electric double layer (EDL) gate specific capacitance (4.16 μF/cm2). Battery drivable low-voltage (1.5 V) transparent EDL thin-film transistors (TFTs) with Al-doped ZnO nanocrystal channel layer gated by such dielectric are fabricated at room-temperature. The TFTs exhibit high-performance n-type transistor characteristics with a high field-effect mobility of 14.9 cm2/V s. The current on/off ratio and subthreshold gate voltage swing are estimated to be 2×106 and 82 mV/decade, respectively. Our results demonstrate that mesoporous SiO2 dielectrics with EDL effect are very promising for battery-powered portable transparent macroelectronics on temperature-sensitive substrates.

High-mobility transparent thin-film transistors with an Sb-doped SnO2 nanocrystal channel fabricated at room temperature.

Transparent thin-film transistors with bottom-gate figure are fabricated by sputter deposition of an Sb-doped SnO2 nanocrystal channel layer onto glass substrates at room temperature with plasma-enhanced chemical vapor deposition SiO2 gate dielectrics and sputtering ITO electrodes. These devices exhibit high-performance n-type transistor characteristics operating in depletion mode with an ultrahigh field-effect mobility of 158 cm(2) V(-1) s(-1). The current on/off ratio and the subthreshold swing are found to be 3 x 10(4) and 0.2 V/decade, respectively. These achievements demonstrate that SnO2-based nanocrystal thin-film transistors are promising for high-speed transparent and flexible electronics on temperature-sensitive substrates.

Degenerate doping induced metallic behaviors in ZnO nanobelts

The authors report the electrical transport properties of an individual degenerately In-doped ZnO (ZnO:In) nanobelts. The room temperature resistivity and electron concentration of the ZnO:In nanobelts are found to be 8.9×10−4 Ω cm and 1.17×1020 cm−3, respectively. The temperature dependent resistivity of the ZnO:In nanobelts agrees well with the Bloch–Gruneisen theory due to the electron-acoustic phonon scattering mechanism. A high failure-current density of 7.4×106 A/cm2 is measured because of the single-crystalline metallic structure.

Individual SnO2 nanowire transistors fabricated by the gold microwire mask method

A gold microwire mask method is developed for the fabrication of transistors based on single lightly Sb-doped SnO(2) nanowires. Damage of the nanowires surface can be avoided without any thermal annealing and surface modification, which is very convenient for the fundamental electrical and photoelectric characterization of one-dimensional inorganic nanomaterials. Transport measurements of the individual SnO(2) nanowire devices demonstrate the high-performance n-type field effect transistor characteristics without significant hysteresis in the transfer curves. The current on/off ratio and the subthreshold swing of the nanowire transistors are found to be 10(6) and 240 mV/decade, respectively.

Low-voltage transparent SnO2 nanowire transistors gated by microporous SiO2 solid-electrolyte with improved polarization response

Low-voltage transparent SnO2 nanowire transistors gated by microporous SiO2 solid-electrolyte are fabricated using a nickel grid as a shadow mask. The operating voltage is found to be as low as 1.5 V due to the large gate capacitance (∼2 μF cm−2) related to the mobile ions-induced electric-double layer (EDL) effect. The polarization mechanism of microporous SiO2 solid electrolytes is studied and three polarizations (EDL formation, ionic migration, and dipole relaxation) at different frequencies are identified. The polarization response is optimized and the improved specific capacitance is 1 μF cm−2 at 1 kHz. The field-effect mobility, current on/off ratio and subthreshold swing are estimated to be 175 cm2 V−1 s−1, 105, and 116 mV/decade, respectively. The static and dynamic bias stress measurements indicate that transparent SnO2 nanowire FETs can operate at low-voltage with highly reproducibility. Such high-performance, low-voltage SnO2 nanowire transistors hold promise for novel device applications, such as portable ion-sensitive sensors.

One-Volt Oxide Thin-Film Transistors on Paper Substrates Gated by

Microporous SiO2 can provide large electric-double-layer (EDL) capacitance and negligible leakage current, owing to lack of electron carrier and limited mobility of mobile ions. The impedance spectroscopy (ionic-conductivity-frequency and capacitance-voltage characteristics) and Fourier-transformed infrared spectroscopy of microporous SiO2 are characterized, which demonstrated that such dielectric is actually a solid-electrolyte dielectric. InGaZnO4 thin-film transistors (TFTs) on paper substrates gated by microporous-SiO2 solid electrolyte are fabricated at room temperature. The large EDL-specific capacitance (1.36 μF/ cm2) results in the paper TFTs operate at a battery-drivable low voltage of 1.0 V. Both depletion-mode (Vth = -0.45 V) and enhancement-mode (Vth = 0.25 V) operations are realized by rationally controlling the oxygen concentration in argon ambient during InGaZnO4 channel deposition. Electrical characteristics with an equivalent field-effect mobility of ~ 21 cm2/V·s, a current on/off ratio of greater than 105, and a subthreshold swing of ~ 80 mV/dec are demonstrated at low frequencies, which are promising for portable paper electronics.