The characteristics and interfacial electronic structures of organic thin film transistor devices with ultrathin (HfO2)x(SiO2)1−x gate dielectrics

Abstract

Pentacene-based thin film transistors with ultrathin (6nm) (HfO2)x(SiO2)1−x gate dielectric layers (x=0.25 and 0.75) were fabricated for low-voltage operation. The devices with ultrathin (HfO2)x(SiO2)1−x as the gate dielectric layer were operated at a gate voltage lower than −4.0eV. However, the threshold voltage and drain current have different values depending on the composition of the (HfO2)x(SiO2)1−x gate dielectric layer. The device with (HfO2)0.75(SiO2)0.25 gate dielectrics, having larger capacitance, shows a higher drain current than that with (HfO2)0.25(SiO2)0.75 gate dielectrics. On the other hand, the device with (HfO2)0.25(SiO2)0.75 gate dielectrics, which has a larger work function, shows a lower threshold voltage. The in situ ultraviolet photoelectron spectroscopy shows that this is caused by the difference in electronic structures and by changes in band alignment of the interface between the pentacene and dielectric layers.

Preparation of Cytocompatible ITO Neuroelectrodes with Enhanced Electrochemical Characteristics Using a Facile Anodic Oxidation Process

“…Further, surface treatments such as acid etching and layer‐by‐layer assembly have been used to modulate and alter the performance of ITO for commercial applications. Electrochemical activation or passivation via the anodic oxidation (anodization process) is widely used in biomedical engineering to grow metal oxide dielectrics for electrical devices and to obtain protective and decorative films on metallic surfaces to increase corrosion resistance . The experimental conditions, i.e., galvanostatic or potentiostatic anodization deposition, electrolyte composition, and deposition time, facilitate the oxidation of ions at the substrate–solution interface to produce thin‐film coatings .…”

Organization of Pentacene Molecules on Anisotropic Ultrathin HfO[sub 2]/Al[sub 2]O[sub 3] Templates for Organic Thin-Film Transistors Using an Ion-Beam Treatment

“…This change in intensity is apparently due to the anisotropic formation at the HfO 2 /Al 2 O 3 surfaces. 7,8 The orientation of the pentacene molecules is affected by this anisotropy when they are deposited on the Hf-O − surface as it interacts strongly with pentacene. This result suggests that IB irradiation could allow for the direct chemical bonding of the activated Hf-O − to the pentacene.…”

“…To obtain a high quality alignment layer, we grow HfO 2 /Al 2 O 3 layers by atomic layer deposition ͑ALD͒, which has the advantages of excellent control of layer thickness as well as good conformity and uniformity. [6][7][8][9] This added buffer layer forms a HfO 2 /Al 2 O 3 dielectric structure, which reduces the negative effects of the bottom interface, such as excessive leakage current or poor gate dielectric reliability. This has an effect not only on the control of the threshold voltage but also on the electronic structure of the interface between the dielectric layers and the organic semiconductor.…”

Tuning the threshold voltage of low voltage organic thin film transistor using light illumination

“…The reported V TH /V on tuning technologies can be divided into two groups: inter-fabrication tuning and post-fabrication tuning. The former includes modifying the interface using self assemble monolayer [2] or ultra-thin polymer film [5], using ionic dielectric [6], employing double-gate device structure [7], changing the device size [8] etc.. And the latter consist of light illumination tuning [9], voltage bias tuning [10], light illumination and voltage bias combination tuning [11,12], and chemical environment tuning [13] etc.. Even though there are so many works about reducing the V op or controlling V TH /V on individually, reports combining these two together, which is critical to low voltage organic circuits, are in lack.…”