Graphene, consisting of a single carbon layer in a two-dimensional (2D) lattice, has been a promising material for application to nanoelectrical devices in recent years. In this study we report the development of a useful ammonia (NH3) gas sensor based on graphene–silver nanowires ‘composite’ with planar electrode structure. The basic strategy involves three steps: (i) preparation of graphene oxide (GO) by modified Hummers method; (ii) synthesis of silver nanowires by polyol method; and (iii) preparation of graphene and silver nanowires on two electrodes using spin and spray-coating of precursor solutions, respectively. Exposure of this sensor to NH3 induces a reversible resistance change at room temperature that is as large as ΔR/R0 ∼ 28% and this sensitivity is eight times larger than the sensitivity of the ‘intrinsic’ graphene based NH3 gas sensor (ΔR/R0 ∼ 3,5%). Their responses and the recovery times go down to ∼200 and ∼60 s, respectively. Because graphene synthesized by chemical methods has many defects and small sheets, it cannot be perfectly used for gas sensor or for nanoelectrical devices. The silver nanowires are applied to play the role of small bridges connecting many graphene islands together to improve electrical properties of graphene/silver nanowires composite and result in higher NH3 gas sensitivity.

No abstract

No abstract

Metal-oxide-semiconductor field effect transistors (MOSFETs) with various doses of La-incorporated in Hafnium-based dielectrics were characterized to evaluate the effect of La on dielectric and device properties. It is found that the Poole-Frenkel emission model could explain our experimental leakage current conduction mechanism reasonably and barrier heights of localized Poole-Frenkel trap sites increase gradually with increasing La incorporation. Cryogenic measurement (from 100 K to 300 K) of MOSFETs reveals that, as the content of La incorporation in the dielectric increases, the more increase of maximum effective mobility has been found at low temperature. It is mainly attributed to the more reduction of phonon scattering due to higher content of La atoms at the interface of dielectric and channel. Though it is relatively small, the existence of La in dielectric reduces coulomb scattering rate as well.

No abstract