Desai Jay A, Adhikari Nirmal, Kaul Anupama B
Department of Metallurgical, Materials and Biomedical Engineering, University of Texas at El Paso El Paso TX 79968 USA
Department of Material Science and Engineering Denton TX 76203 USA.
RSC Adv. 2019 Aug 16;9(44):25805-25816. doi: 10.1039/c9ra03644j. eCollection 2019 Aug 13.
In the present work, various chemical exfoliation routes for semiconducting two-dimensional (2D) layered material WS are explored, which include magnetic stirring (MS), shear mixing (SM), and horn-tip (HT) sonication. Current-voltage measurements, Raman spectroscopy, and photoluminescence (PL) spectroscopy were used to characterize the drop-casted WS nanosheets produced by these three techniques and our analysis revealed that HT sonication produced the most optimal dispersions. Heterostructure photodetector devices were then fabricated using inkjet printing of the HT sonicated dispersions of WS and graphene. The photodetector device performance was measured using a stream of ON/OFF light pulses generated using a red laser with wavelength ∼ 660 nm, and an arbitrary waveform generator. From this analysis, the photoresponsivity and detectivity of the graphene-WS-graphene heterostructure devices were calculated to be ∼0.86 A W and ∼10 Jones, respectively. Capacitance-voltage (-) and -frequency () measurements were also conducted, where the was swept from -6 V to +6 V, while the change in was measured from ∼ 20 kHz up to 3 MHz to gain insights into the nature of the graphene-WS interface. From the - measurements, the plateaued at ∼324.3 pF from ∼-4 V to +4 V for the lowest of 20 kHz and it reduced to ∼200 pF from -6 V to ∼-4 V, and similarly from ∼4 V to 6 V, was ∼190 pF. The decrease in for > +4 V and < -4 V was attributed to the reduction of the interfacial barrier at the electrodes which is suggestive of a Schottky-based photodiode at the graphene-WS interface. A sharp decrease in from ∼315.75 pF at 25.76 kHz to ∼23.79 pF at 480 kHz (at 0 V bias) from the - measurements suggests a strong effect of interface trap density on built-up at the graphene-WS interface and the ensuing Schottky barrier height. Our work confirms the excellent potential of solution-cast, trilayer graphene-WS-graphene heterostructures as a promising photodetector platform using additively manufactured inkjet printing.
在本工作中，探索了用于半导体二维（2D）层状材料WS的各种化学剥离途径，其中包括磁力搅拌（MS）、剪切混合（SM）和喇叭尖（HT）超声处理。使用电流-电压测量、拉曼光谱和光致发光（PL）光谱对通过这三种技术制备的滴铸WS纳米片进行表征，我们的分析表明，HT超声处理产生了最理想的分散体。然后使用喷墨打印HT超声处理的WS和石墨烯分散体制备异质结构光电探测器器件。使用由波长约660 nm的红色激光和任意波形发生器产生的开/关光脉冲流测量光电探测器器件的性能。通过该分析，计算出石墨烯-WS-石墨烯异质结构器件的光响应度和探测率分别约为0.86 A/W和约10琼斯。还进行了电容-电压（-）和-频率（）测量，其中将从-6 V扫描到+6 V，同时测量从约20 kHz到3 MHz的变化，以深入了解石墨烯-WS界面的性质。从-测量结果来看，在最低频率20 kHz时，从约-4 V到+4 V，约为324.3 pF并趋于平稳，从-6 V到约-4 V以及类似地从约4 V到6 V，约为190 pF。对于> +4 V和< -4 V时的降低归因于电极处界面势垒的降低，这表明在石墨烯-WS界面处存在基于肖特基的光电二极管。从-测量结果来看，在0 V偏压下，从25.76 kHz时的约315.75 pF急剧下降到480 kHz时的约23.79 pF，这表明界面陷阱密度对在石墨烯-WS界面处积累的以及随之而来的肖特基势垒高度有很强的影响。我们的工作证实了溶液浇铸的三层石墨烯-WS-石墨烯异质结构作为使用增材制造喷墨打印的有前景的光电探测器平台的巨大潜力。
