Wen Dianzhong

High Sensitivity Magnetic Field Sensors Based on Nano-Polysilicon Thin-Film Transistors

A high-sensitivity magnetic field sensor based on the nano-polysilicon thin film transistors is proposed to adopt the nano-polysilicon thin films and the nano-polysilicon/single silicon heterojunction interfaces as the sensing layers. By using CMOS technology, the fabrication of the nano-polysilicon thin film transistors with Hall probes can be achieved on the 〈100〉 high resistivity single silicon substrates, in which the thicknesses of the nano-polysilicon thin films are 120 nm and the length width ratio of the channel is 320 μm/80 μm. When VDS = 5.0 V, the magnetic sensitivity and linearity is 264 mV/T and 0.23%f.s. (full scale), respectively. The experimental results show that the magnetic sensors based on nano-polysilicon thin film transistors with Hall probes exhibit high sensitivity.

Fabrication and characteristics of the nc-Si/c-Si heterojunction MAGFET

A MAGFET using an nc-Si/c-Si heterojunction as source and drain was fabricated by CMOS technology, using two ohm-contact electrodes as Hall outputs on double sides of the channel situated 0.7L from the source. The experimental results show that when VDS = –7.0 V, the magnetic sensitivity of the single nc-Si/c-Si heterojunction magnetic metal oxide semiconductor field effect transistor (MAGFET) with an L : W ratio of 2 : 1 is 21.26 mV/T, and that with an L : W ratio of 4 : 1 is 13.88 mV/T. When the outputs of double nc-Si/c-Si heterojunction MAGFETs with an L : W ratio of 4 : 1 are in series, their magnetic sensitivity is 22.74 mV/T, which is an improvement of about 64% compared with that of a single nc-Si/c-Si heterojunction MAGFET.

Differential Structure and Characteristics of a New-Type Silicon Magnetic Sensitivity Transistor

A differential structure magnetic sensor is proposed. It is comprised of two new-type silicon magnetic sensitivity transistors (SMSTs) with similar characteristics and has a common emitter, two bases and two collectors. The sensor is fabricated by micro electromechanical system technology on a (100) high resistivity silicon wafer. At room temperature, when supply voltage VDD = 10.0 V, all the base currents Ib1 of SMST1 and Ib2 of SMST2 equal 6.0 mA, the absolute magnetic sensitivity for the two SMSTs are 46.8 mV/kG and 56.1 mV/kG, respectively, and the absolute magnetic sensitivity for the sensor is 102.9 mV/kG. Meanwhile, the temperature coefficient αV of the collector output voltage of the sensor is 0.044%/°C. The experimental results show that the magnetic sensitivity and the temperature characteristics of the sensor can be improved and ameliorated compared with a single SMST.

Fabrication and characteristics of magnetic field sensors based on nano-polysilicon thin-film transistors

A magnetic field sensor based on nano-polysilicon thin films transistors (TFTs) with Hall probes is proposed. The magnetic field sensors are fabricated on 〈100〉 orientation high resistivity (ρ > 500 Ωcm) silicon substrates by using CMOS technology, which adopt nano-polysilicon thin films with thicknesses of 90 nm and heterojunction interfaces between the nano-polysilicon thin films and the high resistivity silicon substrates as the sensing layers. The experimental results show that when VDS = 5.0 V, the magnetic sensitivities of magnetic field sensors based on nano-polysilicon TFTs with length—width ratios of 160 μm/80 μm, 320 μm/80 μm and 480 μm/80 μm are 78 mV/T, 55 mV/T and 34 mV/T, respectively. Under the same conditions, the magnetic sensitivity of the obtained magnetic field sensor is significantly improved in comparison with a Hall magnetic field sensor adopting silicon as the sensing layers.

Fabrication and characterization of the split-drain MAGFET based on the nano-polysilicon thin film transistor

A split-drain magnetic field-effect transistor (MAGFET) based on a nano-polysilicon thin film transistor (TFT) is proposed, which contains one source, two drains and one gate. The sensor chips were fabricated on (100) high resistivity silicon substrate by CMOS technology. When drain—source voltage equals 5.0 V and length and width ratio of the TFT channel is 80 μm/160 μm, the current and voltage magnetic sensitivities of the split-drain MAGFET based on the TFT are 0.018 mA/T and 55 mV/T, respectively. Through adopting nano-polysilicon thin films and nano-polysilicon thin films/high resistivity silicon heterojunction interfaces as the magnetic sensing layers, it is possible to realize detection of the external magnetic field. The test results show that magnetic sensitivity of the split-drain MAGFET can be improved significantly.

The Storage Cell Circuit with Memristor Characteristics of Poly(N-Vinylcarbazole) Films

A kind of non-conjugated polymer memory material, poly(N-vinylcarbazole), is used to investigate silicon-based storage performance with the fact that the one-bit storage cell circuit consists of a sandwiched indium-tinoxide/poly(N-vinylcarbazole)/Al and an n-type metal-oxide-semiconductor field effect transistor. The memristor on the basis of a nano poly(N-vinylcarbazole) film exhibits electrical bistability and flash memory features, for which the switching-on voltage is −1 V and the on/off current ratio approaches 104. At ambient temperature, the memory circuit possesses higher reliability within the programming time 104 s. The output voltage is close to 0.5 V during logic 1, while it is approximately 14 mV in the logic 0. This paves the way for the study on the technology concerning the binary encoding and data storage of nonvolatile memories.