The microscopic process of oxidative etching of two-dimensional molybdenum disulfide(2D MoS_2) at an atomic scale is investigated using a correlative transmission electron microscope(TEM)-etching study.MoS_2 flakes on...The microscopic process of oxidative etching of two-dimensional molybdenum disulfide(2D MoS_2) at an atomic scale is investigated using a correlative transmission electron microscope(TEM)-etching study.MoS_2 flakes on graphene TEM grids are precisely tracked and characterized by TEM before and after the oxidative etching. This allows us to determine the structural change with an atomic resolution on the edges of the domains, of well-oriented triangular pits and along the grain boundaries. We observe that the etching mostly starts from the open edges, grain boundaries and pre-existing atomic defects.A zigzag Mo edge is assigned as the dominant termination of the triangular pits, and profound terraces and grooves are observed on the etched edges. Based on the statistical TEM analysis, we reveal possible routes for the kinetics of the oxidative etching in 2D MoS_2, which should also be applicable for other 2D transition metal dichalcogenide materials like MoSe_2 and WS_2.展开更多
Transferring MoS2 films from growth substrates onto target substrates is a critical issue for their practical applications. Moreover, it remains a great challenge to avoid sample degradation and substrate destruction,...Transferring MoS2 films from growth substrates onto target substrates is a critical issue for their practical applications. Moreover, it remains a great challenge to avoid sample degradation and substrate destruction, because the current transfer method inevitably employs a wet chemical etching process. We developed an etching-free transfer method for transferring MoS2 films onto arbitrary substrates by using ultrasonication. Briefly, the collapse of ultrasonication-generated microbubbles at the interface between polymer-coated MoS2 film and substrates induce sufficient force to delaminate the MoS2 films. Using this method, the MoS2 films can be transferred from all substrates （silica, mica, strontium titanate, and sapphire） and retains the original sample morphology and quality. This method guarantees a simple transfer process and allows the reuse of growth substrates, without involving any hazardous etchants. The etching-free transfer method is likely to promote broad applications of MoS2 in photodetectors.展开更多
A single-mask dry-release process for fabrication of high aspect ratio SOI MEMS devices is presented,which takes advantage of the lag effect in silicon DRIE(deep reactive ion etching).The wide trenches and the releasi...A single-mask dry-release process for fabrication of high aspect ratio SOI MEMS devices is presented,which takes advantage of the lag effect in silicon DRIE(deep reactive ion etching).The wide trenches and the releasing holes are etched to the buried oxide in the first-step DRIE whereas the narrow trenches are still connected due to the lag effect.After the buried oxide is removed by wet etching through the opened releasing holes and wide trenches,the narrow trenches are etched through by the second-step DRIE.Not only can the sticking problems be avoided,but also the footing effect during the DRIE can be partially suppressed.The feasibility of the proposed technique was verified by implementing a capacitive accelerometer.The scale factor and the non-linearity of the fabricated accelerometer were measured to be 63.4 mV/g and 0.1% with the measurement range of ±1 g,respectively.展开更多
基金supported by the National Basic Research Program of China(2014CB932500,2015CB921004)the National Natural Science Foundation of China(51472215,51222202,61571197 and 61172011)the 111 project(B16042)
文摘The microscopic process of oxidative etching of two-dimensional molybdenum disulfide(2D MoS_2) at an atomic scale is investigated using a correlative transmission electron microscope(TEM)-etching study.MoS_2 flakes on graphene TEM grids are precisely tracked and characterized by TEM before and after the oxidative etching. This allows us to determine the structural change with an atomic resolution on the edges of the domains, of well-oriented triangular pits and along the grain boundaries. We observe that the etching mostly starts from the open edges, grain boundaries and pre-existing atomic defects.A zigzag Mo edge is assigned as the dominant termination of the triangular pits, and profound terraces and grooves are observed on the etched edges. Based on the statistical TEM analysis, we reveal possible routes for the kinetics of the oxidative etching in 2D MoS_2, which should also be applicable for other 2D transition metal dichalcogenide materials like MoSe_2 and WS_2.
基金Acknowledgements This work was financially supported by the National Natural Science Foundation of China （Nos. 51222201, 51290272, 51472008, and 51432002）, the National Basic Research Program of China （Nos. 2012CB921404, 2013CB932603, 2012CB933404, and 2011CB921903）, and the Foundation for Innovative Research Groups of the National Natural Science Foundation of China （No. 51121091）.
文摘Transferring MoS2 films from growth substrates onto target substrates is a critical issue for their practical applications. Moreover, it remains a great challenge to avoid sample degradation and substrate destruction, because the current transfer method inevitably employs a wet chemical etching process. We developed an etching-free transfer method for transferring MoS2 films onto arbitrary substrates by using ultrasonication. Briefly, the collapse of ultrasonication-generated microbubbles at the interface between polymer-coated MoS2 film and substrates induce sufficient force to delaminate the MoS2 films. Using this method, the MoS2 films can be transferred from all substrates （silica, mica, strontium titanate, and sapphire） and retains the original sample morphology and quality. This method guarantees a simple transfer process and allows the reuse of growth substrates, without involving any hazardous etchants. The etching-free transfer method is likely to promote broad applications of MoS2 in photodetectors.
基金supported by the National Natural Science Foundation of China (Grant No. 90923037)
文摘A single-mask dry-release process for fabrication of high aspect ratio SOI MEMS devices is presented,which takes advantage of the lag effect in silicon DRIE(deep reactive ion etching).The wide trenches and the releasing holes are etched to the buried oxide in the first-step DRIE whereas the narrow trenches are still connected due to the lag effect.After the buried oxide is removed by wet etching through the opened releasing holes and wide trenches,the narrow trenches are etched through by the second-step DRIE.Not only can the sticking problems be avoided,but also the footing effect during the DRIE can be partially suppressed.The feasibility of the proposed technique was verified by implementing a capacitive accelerometer.The scale factor and the non-linearity of the fabricated accelerometer were measured to be 63.4 mV/g and 0.1% with the measurement range of ±1 g,respectively.
