Papers by Keyword: Hydrogen Annealing

Abstract: In the applications of renewable energy; use of energy in the electric vehicles and many other electronic devices such as mobile devices and computers; electrical energy storage is essential. Batteries are used to store electrical energy but have low power density and lower cycle life. Using extremely porous electrode materials for supercapacitors, based on quick ion transport, are specialized to provide high power density, long stability and effective energy storage. Using graphene-based electrode is the best way to boost the energy density of supercapacitor. Graphene synthesized by chemical exfoliation, ultrasonic exfoliation and solution based chemical reduction suffers agglomerations that tends to restack the graphene sheets. In the present work, we studied the option of hydrogen gas annealing to obtain graphene from amorphous carbon film, coated on Cu substrate using sputtering. For electrochemical assessment, in situ developed film was compared with graphene applied from other methods of graphene synthesis. Atomic force microscopy (AFM) results revealed that annealed carbon sputtered electrode has high route mean square (RMS) roughness i.e 181.5 nm, most probably because of graphene formation. Cyclic voltammogram (CV) results show less area curve for annealed electrode which depicts high active area for charge storage and enhanced conductivity due to deposited graphene layer.

Abstract: 4H-SiC MOSFET on carbon face exhibits the high channel mobility when the gate oxide is formed by pyrogenic wet oxidation. However, this improvement is not proof against the metallization annealing which is indispensable in the fabrication of the SiC power MOSFETs. We develop the alternative metallization process suitable for the high channel mobility on the carbon face. The metallization annealing in hydrogen ambient has much effect to suppress the degradation of the channel mobility. The lateral MOSFET with the ohmic contact formed by hydrogen annealing exhibits the high channel mobility which is comparable to the channel mobility of the lateral MOSFET formed without metallization annealing.

Abstract: Various annealing conditions after film deposition have a great effect on electrical and structural properties of low-k films. In this work, we studied hydrogen atmosphere heat treatment effect on low-k films. After the room temperature deposition of a-SiOC:H low-k films following post-deposition-annealing (PDA) for 30 min. at 450°C in an N2 ambient, final annealing was performed for 30 min. at 400°C in an N2, a forming gas 1 (5% H2 + 95% N2), and a forming gas 2 (10% H2 + 90% N2) ambient. The flat band voltage was shifted toward the ideal value of 0.61V after two forming gas anneals, but it increased k values of the films. It was ascribed that hydrogen effectively substitutes defect sites or structural imperfections of low-k films and makes the film more hydrophilic. The FT-IR, XPS analyses and the contact angle measurement supported our conclusion.

Abstract: Atomic Layer Deposited Al2O3 films on hydrogen-terminated 6H-SiC(0001) were annealed in hydrogen atmosphere and characterized by admittance spectroscopy measurement and photoelectron spectroscopy (PES). The resultant density of interface trap (Dit) from admittance spectroscopy measurement is reduced near mid gap, but increases strongly towards the conduction band edge. Systematic PES measurements show that hydrogen annealing introduces Si4+ as a new component besides Si0 and Si+. Using different electron escape depths for photon electrons, depth profiling of Si in its different oxidation states was performed. The result indicates the formation of a top SiO2 layer and a rougher interfacial layer containing more Si+ and Si4+ which could be responsible for the strong increase of Dit just below the conduction band edge.

Abstract: We investigated the effects of hydrogen annealing process on ferroelectricity in SrBi₂Ta₂O₉(SBT) capacitors. The hydrogen-induced degradation of SBT capacitors was found after a hydrogen annealing process. The degraded properties could be recovered by re-crystallization annealing process in O₂ ambient for 30 min. In order to prevent the catalyst reaction of Pt electrode known as an origin of hydrogen-induced degradation, Au top electrode was used. It was confirmed that Au electrode effectively prevented capacitors from degrading during hydrogen process.