Effects of interfacial oxide layers of the electrode metals on the electrical characteristics of organic thin-film transistors with HfO2 gate dielectric

Abstract

Articles you may be interested inAtomic layer deposition grown metal-insulator-metal capacitors with RuO 2 electrodes and Al-doped rutile TiO 2 dielectric layer J. Vac. Sci. Technol. B 29, 01AC09 (2011); 10.1116/1.3534023 Electrode effects on the conduction mechanisms in HfO 2 -based metal-insulator-metal capacitors Characteristics of metal-insulator-semiconductor capacitors based on high-k HfAlO dielectric films obtained by low-temperature electron-beam gun evaporation Appl. Phys. Lett. 85, 5950 (2004); 10.1063/1.1836875Metal-insulator-metal capacitors using Y 2 O 3 dielectric grown by pulsed-injection plasma enhanced metalorganic chemical vapor deposition HfO 2 -based devices employing various electrode metals (Al, W, Pt, Cu, and Cr) were fabricated and characterized in order to examine the importance of the choice of metal electrode when sputter-depositing HfO 2 films. It was found that metal-insulator-metal capacitors with an Al bottom electrode exhibit a significantly smaller leakage current and a larger breakdown field strength than devices using W, Pt, Cu, and Cr electrodes. By examining HfO 2 /metal interfaces with x-ray photoelectron spectroscopy, it was found that metal electrodes are oxidized during the deposition of HfO 2 , resulting in interfacial oxide layers of the electrode metals (Al 2 O 3 , WO 3 , PtO, CuO, and Cr 2 O 3 þ CrO 3 ) between the metal electrode and the HfO 2 layer. The formation of a metal oxide interlayer is a consequence of the high-energy oxygen ions generated during HfO 2 sputtering. The difference in the device performance was attributed to the electronic properties of the oxide interlayers. It was found that when the oxide interlayers are semiconducting (e.g., WO 3 , PtO, CuO, or Cr 2 O 3 þ CrO 3 ), devices have high leakage currents and low breakdown field strengths, and an insulating oxide interlayer (Al 2 O 3 ) enhances these device characteristics. Organic thin-film transistors (OTFTs) using a HfO 2 dielectric layer showed that an Al gate has a much lower offstate current, larger on/off ratio, and smaller sub-threshold slope compared with OTFTs using a Cr electrode. These results demonstrate the importance of the metal gate electrode and the electrical characteristics of its oxide when using the sputter-deposition of HfO 2 to fabricate thin-film transistors.

Atomic View of Filament Growth in Electrochemical Memristive Elements

“…The barrier height for electron transmission was assigned to 2.0 eV, which was estimated from the I-V curve of a fresh device with a known barrier width of 3 nm ( Figure S7 ). Although the real situation is more complex than the fresh state, the value of the barrier height was reasonable and comparable with the reported results 37 38 39 . Another parameter related to tunnel resistance is the area of the filament tip.…”

Monolayer Molybdenum Disulfide Transistors with Single-Atom-Thick Gates

“…Figure a shows the measured leakage current through graphene-gated devices with TiO 2 /HfO 2 gate dielectric stack. When the thickness of HfO 2 ( t Hf ) was 16 nm (Figure S2a) or the total oxide thickness ( t ox ) was 17.2 nm, the gate leak current remained below 10 pA before the breakdown of the dielectric at a gate bias of 10 V. This breakdown field of 0.58 V/nm (Figure b) is close to the breakdown field of ALD oxide on polished Si substrates and approximately twice the value measured with metal bottom gate (Figure S2b and ref ). Upon decrease of the HfO 2 thickness, the breakdown field increased: when t Hf was 4 nm or t ox was 5.2 nm, the breakdown field was increased to 1 V/nm (Figure b), in agreement with a previously reported value .…”

Polymer‐modified solution‐processed metal oxide dielectrics on aluminum foil substrate for flexible organic transistors

“…Recently, metal oxide dielectric materials have gain interest among researchers because of good electrical and optical properties . Oxide dielectrics can be deposited by sputtering, atomic layer deposition (ALD), sol–gel, and spray methods . Among these approaches, solution‐processed methods are much more attractive compared with the other methods, which can notably decrease the manufacturing cost of the devices.…”