Xiangjian Meng

Ultrasensitive and Broadband MoS2 Photodetector Driven by Ferroelectrics

A few-layer MoS2 photodetector driven by poly(vinylidene fluoride-trifluoroethylene) ferroelectrics is achieved. The detectivity and responsitivity are up to 2.2 × 10(12) Jones and 2570 A W(-1), respectively, at 635 nm with ZERO gate bias. E(g) of MoS2 is tuned by the ultrahigh electrostatic field from the ferroelectric polarization. The photoresponse wavelengths of the photodetector are extended into the near-infrared (0.85-1.55 μm).

Giant Negative Electrocaloric Effect in Antiferroelectric La‐Doped Pb(ZrTi)O3 Thin Films Near Room Temperature

Antiferroelectric thin films are demonstrated as a new class of giant electrocaloric materials that exhibit a negative electrocaloric response of about -5 K near room temperature. The giant negative electrocaloric effect may open up a new paradigm for light, compact, reliable, and high-efficiency refrigeration devices.

Mn-doped 0.71Pb(Mg1∕3Nb2∕3)O3–0.29PbTiO3 pyroelectric crystals for uncooled infrared focal plane arrays applications

3mol%Mn-doped 0.71Pb(Mg1∕3Nb2∕3)O3–0.29PbTiO3 single crystals were grown by a modified Bridgman technique. The pyroelectric properties and thermal stability of the crystals were investigated. Mn substitution resulted in an enhanced pyroelectric coefficient and a lower dielectric loss, which led to the improvement of the detectivity figure of merit of doped crystals by about a factor of 4 at 50Hz compared with that of pure crystals. Moreover, the thermal stability was enhanced by Mn substitution. The mechanism of doping effect is explained by the fact that the domain walls are pinned by the dopant dipolar defects, which optimizes the pyroelectric performance of 0.71Pb(Mg1∕3Nb2∕3)O3–0.29PbTiO3 for uncooled infrared focal plane arrays applications.

Large pyroelectric response in relaxor-based ferroelectric (1−x)Pb(Mg1∕3Nb2∕3)O3–xPbTiO3 single crystals

The pyroelectric properties of (1−x)Pb(Mg1∕3Nb2∕3)O3–xPbTiO3 (PMN–xPT) single crystals have been investigated over a broad composition range of 0.13⩽x⩽0.40. The best pyroelectric performances are achieved in ⟨111⟩-oriented PMN–0.26PT single crystal. At room temperature, the figures of merit for voltage responsivity and detectivity reach up to 0.11m2∕C and 15.3×10−5Pa−1∕2, respectively. These properties are superior to those of conventional pyroelectric ceramics that have been widely used in device applications. PMN–0.26PT single crystal also possesses a relative high Curie temperature (∼120°C) and a low thermal diffusivity (∼4.4×10−7m2∕s). Furthermore, the pyroelectric properties of PMN–xPT (x⩾0.26) single crystals are weak dependent on temperature and nearly independent of frequency in the experimental temperature range of 20–55°C and frequency range of 50–10000Hz. The superior pyroelectric performances of the single crystal make it a promising candidate for high-performance uncooled infrared detectors a...

Domain stabilization effect of interlayer on ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymer ultrathin film

A charge injection material, poly(3,4-ethylene dioxythioohene)-poly(styrene sulfonic) acid, is introduced as a buffer layer between metal electrodes and a ferroelectric poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer ultrathin film. The buffer layer not only prevents the reactions between P(VDF-TrFE) layer and the top electrode during metallization process, which leads to the loss of polarization, but also supplies the amount of charges needed for compensation of the ferroelectric dipoles to stabilize the domain during switching process so that the fatigue property was improved tremendously. The sandwiched structure shows prominent ferroelectric properties in a 50 nm P(VDF/TrFE) film. A coercive electric field of 52 MV/m and a remnant polarization of 88 mC/m2 are recorded. With two additional organic interlayers, 33 nm thick in total, the coercive field decreases. After more than 1×107 cycles of switching, the polarization remains as high as 68 mC/m2. Moreover, the cell still has good ...

When Nanowires Meet Ultrahigh Ferroelectric Field–High-Performance Full-Depleted Nanowire Photodetectors

One-dimensional semiconductor nanowires (NWs) have been widely applied in photodetector due to their excellent optoelectronic characteristics. However, intrinsic carrier concentration at certain level results in appreciable dark current, which limits the detectivity of the devices. Here, we fabricated a novel type of ferroelectric-enhanced side-gated NW photodetectors. The intrinsic carriers in the NW channel can be fully depleted by the ultrahigh electrostatic field from polarization of P(VDF-TrFE) ferroelectric polymer. In this scenario, the dark current is significantly reduced and thus the sensitivity of the photodetector is increased even when the gate voltage is removed. Particularly, a single InP NW photodetector exhibits high-photoconductive gain of 4.2 × 10(5), responsivity of 2.8 × 10(5) A W(-1), and specific detectivity (D*) of 9.1 × 10(15) Jones at λ = 830 nm. To further demonstrate the universality of the configuration we also demonstrate ferroelectric polymer side-gated single CdS NW photodetectors with ultrahigh photoconductive gain of 1.2 × 10(7), responsivity of 5.2 × 10(6) A W(-1) and D* up to 1.7 × 10(18) Jones at λ = 520 nm. Overall, our work demonstrates a new approach to fabricate a controllable, full-depleted, and high-performance NW photodetector. This can inspire novel device structure design of high-performance optoelectronic devices based on semiconductor NWs.

Growth and pyroelectric properties of high Curie temperature relaxor-based ferroelectric Pb(In1∕2Nb1∕2)O3–Pb(Mg1∕3Nb2∕3)O3–PbTiO3 ternary single crystal

To enhance the service temperature of relaxor-PbTiO3 pyroelectric single crystals, high quality ternary perovskite single crystal was grown by a modified Bridgman technique. Analyzed by x-ray fluorescence, the as-grown crystal is 0.41Pb(In1∕2Nb1∕2)O3–0.17Pb(Mg1∕3Nb2∕3)O3–0.42PbTiO3 [PIMNT(41/17/42)], which appears to be a tetragonal ferroelectric phase with relatively high Curie temperature of 253°C. It exhibits the relative permittivity of 487 and low dielectric loss of 0.3% at 50Hz and room temperature. The pyroelectric properties with a pyroelectric coefficient of 5.7×10−4C∕m2K and a detectivity of 6.34×10−5Pa−1∕2 would satisfy the needs of operation as a high Curie temperature material. The results show that PIMNT crystal with better temperature stability, compared with the pure PMNT single crystals, is a good candidate as an infrared detector material.

Processing optimization and sintering time dependent magnetic and optical behaviors of Aurivillius Bi5Ti3FeO15 ceramics

Aurivillius Bi5Ti3FeO15 (BTF) ceramics were synthesized using the conventional solid state reaction method by optimizing excess of Bi2O3 and sintering time. Their structures, magnetic, and optical properties were investigated in detail. The optimum process to sinter pure Aurivillius BTF ceramics was confirmed to be 3 wt. % excess Bi2O3 to compensate the Bi volatilization at 1050 °C for 240 min (BTF-240M). The microstructure and crystalline structure of the BTF ceramics had little dependence on the sintering time from the x-ray diffraction (XRD) and scanning electron microscopic data. Nevertheless, the magnetic and optical properties were closely related with the sintering time. The overall magnetic behavior of these BTF ceramics was superparamagnetic (SPM), whereas there were unambiguous clues for the existence of antiferromagnetic (AFM) interactions. However, whether the SPM behavior was intrinsic or arised from a tiny amount of spinel Fe3O4 impurity phase cannot be thoroughly ruled out in the XRD detect...

Synthetically controlling the optoelectronic properties of dithieno[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b′]dithiophene-alt-diketopyrrolopyrrole-conjugated polymers for efficient solar cells

We have demonstrated that, by changing the substituent groups on dithieno[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b′]dithiophene (DTBDT), one could effectively and rationally tune the energy levels, optical band gaps and charge transporting properties, etc. of the DTDBT derivatives (DTBDTs) and their conjugated polymers (CPs) and diketopyrrolopyrrole (DPP) derivatives.

Highly sensitive phototransistor based on GaSe nanosheets

Phototransistors based on two dimensional semiconductors have drawn increasing attention in recent years. GaSe is a typical semiconductor with a layered structure. In this work, the ultrathin GaSe nanosheets were exfoliated from commercially available crystals using a micromechanical cleavage technique. Then, the nanosheets were used to fabricate field effect transistors (FETs) on Si/SiO2 substrates with interdigitated electrodes. The electrical and optoelectronic properties of the FET were characterized. The phototransistor based on a GaSe nanosheet had a high photoresponsivity (∼2200 mA/W) and a high Iphoto/Idark (photoresponse current over dark current) ratio of almost 103.