Device performance enhancement via a Si-rich silicon oxynitride buffer layer for the organic photodetecting device

Multilevel Bipolar Electroforming-Free Resistive Switching Memory Based on Silicon Oxynitride

Resistive random-access memory (RRAM) devices are fabricated by utilizing silicon oxynitride (SiOxNy) thin film as a resistive switching layer. A SiOxNy layer is deposited on a p+-Si substrate and capped with a top electrode consisting of Au/Ni. The SiOxNy-based memory device demonstrates bipolar multilevel operation. It can switch interchangeably between all resistance states, including direct SET switching from a high-resistance state (HRS) to an intermediate-resistance state (IRS) or low-resistance state (LRS), direct RESET switching process from LRS to IRS or HRS, and SET/RESET switching from IRS to LRS or HRS by controlling the magnitude of the applied write voltage signal. The device also shows electroforming-free ternary nonvolatile resistive switching characteristics having RHRS/RIRS > 10, RIRS/RLRS > 5, RHRS/RLRS > 103, and retention over 1.8 × 104 s. The resistive switching mechanism in the devices is found to be combinatory processes of hopping conduction by charge trapping/detrapping in the bulk SiOxNy layer and filamentary switching mode at the interface between the SiOxNy and Ni layers.

The role of defects in organic image sensors for green photodiode

Controlling defect states in a buffer layer for organic photo devices is one of the vital factors which have great influence on the device performance. Defect states in silicon oxynitride (SiO_xN_y) buffer layer for organic photo devices can be controlled by introducing appropriate dopant materials. We performed ab initio simulations to identify the effect on doping SiO_xN_y with carbon (C), boron (B), and phosphorous (P) atoms. The results unveil that hole defects in the SiO_xN_y layer diminish with the phosphorous doping. Based on the simulation results, we fabricate the small molecule organic photodetector (OPD) including the phosphorous-doped SiO_xN_y buffer layer and the active film of blended naphthalene-based donor and C60 acceptor molecules, which shows excellent enhancement in the external quantum efficiency (EQE). The results of our charge-based deep level transient spectroscopy (Q-DLTS) measurements confirmed that the EQE enhancement originates from the decrease of the hole traps induced by the reduced hole defects. The method of controlling the defect states in SiO_xN_y buffer layers by the doping can be used to improve the performance in various organic photo devices.

Surface conversion of ZnO nanorods to ZIF-8 to suppress surface defects for a visible-blind UV photodetector

ZnO nanomaterials are promising building blocks for an efficient UV photodetector; however, their slow sensing behavior and undesired response to visible light, which are attributed to surface defects, such as oxygen or zinc vacancies, are challenges that remain to be addressed. Here, we transformed the ZnO nanorod surface into a zeolitic imidazolate framework-8 (ZIF-8) to eliminate ZnO surface defects. Vertical-type photodetectors were fabricated incorporating a Schottky junction at the ZIF-8/gold (Au) top electrode and could respond to UV light with a rapid response and recovery (1-2 s) and demonstrated a UV-to-visible rejection ratio in the order of 10³, qualifying them as efficient visible-blind UV photodetectors. It is noteworthy that the ZIF-8 layer effectively separated the photogenerated electron-hole pairs, and thus reduced their recombination probability. The enhanced photodetector displayed excellent figures-of-merit: a responsivity of 291 A W^-1 and a detectivity of 5.9 × 10¹³ cm Hz^1/2 W^-1 under illumination at 295 nm.

Synthesis of a Novel Polyethoxysilsesquiazane and Thermal Conversion into Ternary Silicon Oxynitride Ceramics with Enhanced Thermal Stability

A novel polyethoxysilsesquiazane ([EtOSi(NH)_1.5]_n, EtOSZ) was synthesized by ammonolysis at −78 °C of ethoxytrichlorosilane (EtOSiCl₃), which was isolated by distillation as a reaction product of SiCl₄ and EtOH. Attenuated total reflection-infra red (ATR-IR), ¹³C-, and ²⁹Si-nuclear magnetic resonance (NMR) spectroscopic analyses of the ammonolysis product resulted in the detection of Si–NH–Si linkage and EtO group. The simultaneous thermogravimetric and mass spectrometry analyses of the EtOSZ under helium revealed cleavage of oxygen-carbon bond of the EtO group to evolve ethylene as a main gaseous species formed in-situ, which lead to the formation at 800 °C of quaternary amorphous Si–C–N with an extremely low carbon content (1.1 wt %) when compared to the theoretical EtOSZ (25.1 wt %). Subsequent heat treatment up to 1400 °C in N₂ lead to the formation of X-ray amorphous ternary Si–O–N. Further heating to 1600 °C in N₂ promoted crystallization and phase partitioning to afford Si₂N₂O nanocrystallites identified by the XRD and TEM analyses. The thermal stability up to 1400 °C of the amorphous state achieved for the ternary Si-O-N was further studied by chemical composition analysis, as well as X-ray photoelectron spectroscopy (XPS) and ²⁹Si-NMR spectroscopic analyses, and the results were discussed aiming to develop a novel polymeric precursor for ternary amorphous Si–O–N ceramics with an enhanced thermal stability.