The impacts of HfO_x inserting layer thickness on the electrical properties of the ZnO-based transparent resistance random access memory(TRRAM) device were investigated in this paper. The bipolar resistive switching behavior of a single ZnO film and bilayer HfO_x/ZnO films as active layers for TRRAM devices was demonstrated. It was revealed that the bilayer TRRAM device with a 10-nm HfO_x inserted layer had a more stable resistive switching behavior than other devices including the single layer device, as well as being forming free, and the transmittance was more than 80% in the visible region. For the HfO_x/ZnO devices, the current conduction behavior was dominated by the space-charge-limited current mechanism in the low resistive state(LRS) and Schottky emission in the high resistive state(HRS), while the mechanism for single layer devices was controlled by ohmic conduction in the LRS and Poole–Frenkel emission in the HRS.
Transition metal dichalcogenides(TMDCs)are promising high performance electronic materials due to their interesting semiconductor properties.However,it is acknowledged that the effective electrical contact between TMDCs-layered materials and metals remains one of the major challenges.In this work,the homogeneous monolayer MoS_(2)films with high crystalline quality were prepared by chemical vapor deposition method on SiO2/Si substrates.The back-gate field-effect transistors(FETs)were fabricated by inserting an ultrathin Al_(2)O_(3)interlayer between the metal electrodes and MoS_(2)nanosheets.With the addition of an ultrathin 0.8 nm Al_(2)O_(3)interlayer,the contact resistance decreased dramatically from 59.9 to 1.3 kΩμm and the Schottky barrier height(SBH)dropped from 102 to 27 meV compared with devices without the Al_(2)O_(3)interlayer.At the same time,the switching ratio increased from~106to~108,and both the on-current and field-effect mobility were greatly improved.We find that the ultrathin Al_(2)O_(3)interlayer can not only reduce the SBH to alleviate the Fermi level pinning phenomenon at the interface,but also protect the channel materials from the influence of air and moisture as a covering layer.In addition,the lattice and band structures of Al_(2)O_(3)/MoS_(2)film were calculated and analyzed by first-principles calculation.It is found that the total density of states of the Al_(2)O_(3)/MoS_(2)film exhibits interfacial polarized metals property,which proves the higher carrier transport characteristics.FETs with Al_(2)O_(3)interlayers have excellent stability and repeatability,which can provide effective references for future low power and high performance electronic devices.
In this letter,the Ta/HfO_x/BN/TiN resistive switching devices are fabricated and they exhibit low power consumption and high uniformity each.The reset current is reduced for the HfO_x/BN bilayer device compared with that for the Ta/HfO_x/TiN structure.Furthermore,the reset current decreases with increasing BN thickness.The HfO_x layer is a dominating switching layer,while the low-permittivity and high-resistivity BN layer acts as a barrier of electrons injection into TiN electrode.The current conduction mechanism of low resistance state in the HfO_x/BN bilayer device is space-chargelimited current(SCLC),while it is Ohmic conduction in the HfO_x device.
We demonstrate the polarization of resistive switching for a Cu/VOx/Cu memory cell.The switching behaviors of Cu/VOx/Cu cell are tested by using a semiconductor device analyzer(Agilent B1500A),and the relative micro-analysis of I-V characteristics of VOx/Cu is characterized by using a conductive atomic force microscope(CAFM).The I-V test results indicate that both the forming and the reversible resistive switching between low resistance state(LRS) and high resistance state(HRS) can be observed under either positive or negative sweep.The CAFM images for LRS and HRS directly exhibit evidence for the formation and rupture of filaments based on positive or negative voltage.The Cu/VOx/Cu sandwiched structure exhibits reversible resistive switching behavior and shows potential applications in the next generation of nonvolatile memory.
We proposed a compact and tunable multimode interferometer(MMI)based on an asymmetric wavy fiber(AMWF),which has axial offset,off-center taper waist,and micro-length.The fabrication process only contains non-axis pulling processes of single-mode fiber on two close positions.Theoretical qualitative analyses and experiments verify the tunable multimode propagation of the AMWF.Experimental results show a nonlinear wavelength response with increasing axis displacement from 0 to 120μm.In the range of 0—10μm,the sensitivity reaches the highest value of-1.33 nm/μm.Owing to its cost-effective,high-compact and tunable multimode propagation properties,the AMWF provides a promising platform for micro-nano photonic devices and optical sensing applications.
LI YuanzhengLI YiMIAO YinpingWANG FangHU KaiZHANG Kailiang
