In-plane exchange bias (EB) in [Pt/Co]n/NiFe/NiO heterostructures with orthogonal easy axes is investigated. The reversible in-plane EB effect at the ferromagnetic (FM)/FM [Pt/Co]n/NiFe interface allows one to manipulate the value and direction of the EB of the heterostructures, which can be induced by applying a magnetic field larger than the perpendicular anisotropy field of the [Pt/Co]n multilayers. The difference between the EB of the heterostructures after field cooling and zero field cooling disappears at 120 K, which may originate from the exchange coupling at the FM/antiferromagnetic (AFM) NiFe/NiO interface. The NiFe thickness dependence of the bias field of the EB exhibits behavior similar to that in conventional FM/AFM bilayers. The EB can be maintained even at room temperature.
Bulk-like molybdenum disulfide (MoS2) thin films were deposited on Si substrates using dc magnetron sputtering technique and n-MoS2/p-Si junctions were fabricated at room temperature (RT) and 400 °C, respectively. The typical oscillating modes of E 1 2g and A1g were shown in the Raman spectra of the as-grown MoS2 films. Atomic force microscopy illustrated that the surfaces of the films were composed of dense nanoscale grains and scanning electron microscopy revealed the existence of large quantities of pores in the surface. The current-voltage curves of the junctions showed obvious rectifying characteristics due to the energy-band bending near the interface of MoS2/Si. The fabricated junctions exhibited humidity-dependent electrical properties. Compared with the one with the MoS2 film deposited at RT, the junction fabricated at 400 °C showed much more obvious sensing properties to humidity gas. Especially, the sensitivity of the device could be tuned by external electrical fields. In the forward voltage range, the currents increased significantly after the junction was exposed to humidity conditions. The response increased with increasing voltage and reached the saturated value after V=1.9 V. The sensing performance was featured by a high sensitivity, fast response and recovery. The junction current in reverse voltage range decreased under the humidity condition. This was contrary to that in forward voltage range. We also studied the dependence of the sensing response on humidity levels. An almost linear correlation was obtained in the measured range of humidity levels. The sensing mechanisms of the MoS2/Si heterojunction were proposed.
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