Gate Insulator For Thin-film Transistors Research Articles

Low-Temperature Processable, Photo-Curable Polyimides as Gate Insulators for Thin-Film Transistors

Low-Temperature Processable, Photo-Curable Polyimides as Gate Insulators for Thin-Film Transistors

Investigation of the ferroelectric switching behavior of P(VDF-TrFE)-PMMA blended films for synaptic device applications

Synaptic plasticity can be mimicked by electronic synaptic devices. By using ferroelectric thin films as gate insulator for thin-film transistors (TFT), channel conductance can be defined as the synaptic plasticity, and gradually modulated by the variations in amounts of aligned ferroelectric dipoles. Poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)]-poly(methyl methacrylate) (PMMA) blended films are chosen and their switching kinetics are investigated by using the Kolmogorov-Avrami-Ishibashi model. The switching time for ferroelectric polarization is sensitively influenced by the amplitude of applied electric field and volumetric ratio of ferroelectric beta-phases in the P(VDF-TrFE)-PMMA films. The switching time of the P(VDF-TrFE) increases with decreasing the pulse amplitude and/or the ratio of ferroelectric beta-phases by incorporation of PMMA. The activation electric field is also found to increase as the increase in blended amount of PMMA. Synapse TFTs are fabricated using the P(VDF-TrFE)-PMMA as gate insulator and In-Ga-Zn-O active channels. The drain currents of the synapse TFTs gradually increased when the voltage pulse signals with given duration are repeatedly applied. This suggests that the synaptic weights can be modulated by the number of external pulse signals, and that the proposed synapse TFT can be applied for mimicking the operations of bio-synapses.

Anodic Oxidation of Nitrogen-Added Al-Based Alloys for Thin-Film Transistors

ABSTRACTNovel anodized films of nitrogen-added aluminum-based alloys were proposed for use in the fabrication of gate insulators for thin-film transistors, and the effect of nitrogen addition on the anodized aluminum-based alloys was investigated. Gadolinium and neodymium were employed as alternative alloy components. The film thickness, the dielectric constant, and the roughness average of the anodized films decreased as the nitrogen content increased, and the nitrogen content was required to be lower than 20 at.%. The most improved values of the breakdown electric fields of anodized aluminum-gadolinium and aluminum-neodymium alloy were 10.1 MV/cm with 6.0 at.% nitrogen content and 9.9 MV/cm with 4.0 at.% nitrogen content, respectively. The leakage currents of the anodized films under a negative bias, which could not be suppressed by high-temperature annealing, were adequately suppressed by nitrogen addition, especially in anodized aluminum-gadolinium alloy. The current leakage of the anodized aluminum-gadolinium alloy with 6.0 at.% nitrogen content became -8E-13 A at -10 V and 150°C. This value is nearly equal to that of chemical-vapor-deposited (CVD) films.

Nanostructure and Electrical Properties of Anodized Al Gate Insulators for Thin-Film Transistors

AbstractA novel anodic oxidation method for aluminum thin-film on the glass substrate is proposed for the fabrication of a gate insulator in thin-film transistor (TFT). A proposed rear-positioned cathode makes for much more smooth surface with an average surface roughness of under 4 nm in comparison with conventional cathode positions. The anodic oxidation conditions were comprehensively investigated. The current density, ethylene glycol concentration, and cathode position were chosen as the elements of anodic oxidation condition matrix, and all these conditions affected the film formation. The surface morphology and nanostructure of the anodized films were characterized with an atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (TEM). Films formed at higher ethylene glycol concentrations of over 50% and higher current densities of over 0.9 mA/cm2 exhibited higher breakdown electric fields of over 7 MV/cm, and lower leakage currents. These films had relatively smooth surfaces and took on the shapes of the underlying aluminum. In contrast, films formed at lower ethylene glycol concentrations of under 50% and lower current densities of under 0.9 mA/cm2 had rough surfaces and microvoids. A high concentration of ethylene glycol increases the cost of mass production, however, the proposed rear-positioned cathode method can be achieved even when the concentration of ethylene glycol is under 50%.

High spatial resolution photo-oxidation of a-Si:C at low temperatures H films

Ultraviolet illumination of hydrogenated amorphous silicon-carbon alloys, a-Si:C:H, produces oxide patterns with a resolution better than 5 mu m. Notably, the photoinduced oxidation occurs at temperatures less than 50 degrees C for a-Si:C:H films with a carbon content>30 atomic %. Possible applications include photolithography, apertured membranes, archival optical storage and gate insulators for thin-film transistors. >