The etching effect of ammonia (NH3) on the growth of vertically aligned nanotubes/nanofibers (CNTs) was investigated by direct-current plasma enhanced chemical vapor deposition (DC-PECVD). NH3 gas etches Ni cata...The etching effect of ammonia (NH3) on the growth of vertically aligned nanotubes/nanofibers (CNTs) was investigated by direct-current plasma enhanced chemical vapor deposition (DC-PECVD). NH3 gas etches Ni catalyst layer to form nanoscale islands while NH3 plasma etches the deposited amorphous carbon. Based on the etching effect of NH3 gas on Ni catalyst, the differences of growing bundles of CNTs and single strand CNTs were discussed; specifically, the amount of optimal NH3 gas etching is different between bundles of CNTs and single strand CNTs. In contrast to the CNT carpet growth, the single strand CNT growth requires shorter etching time (5 min) than large catalytic patterns (10 rain) since nano dots already form catalyst islands for CNT growth. Through removing the plasma pretreatment process, the damage from being exposed at high temperature substrate occurring during the plasma generation time is minimized. High resolution transmission electron microscopy (HTEM) shows fishbone structure of CNTs grown by PECVD.展开更多
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
Patterned ferromagnetic thin film shows promising applications in ultra-high density magnetic storage,magnetoresistive transducer,magnetic random access memory and many other devices.Since the performance of these dev...Patterned ferromagnetic thin film shows promising applications in ultra-high density magnetic storage,magnetoresistive transducer,magnetic random access memory and many other devices.Since the performance of these devices is closely associated with the magnetic properties of the etched patterns,it is necessary to study the effects of freshly etched surface oxidation on the magnetic properties of the patterned microstructures.In the current work,were carried out an X-ray Magnetic Circular Dichroism(XMCD) study on a 50 nm Co 0.9 Fe 0.1 continuous thin film and a related patterned Co 0.9 Fe 0.1 grating structure etched with a 2 μm period.Based on the sum rules,the spin and orbital moments were calculated for these two samples,respectively.The results indicated that the spin and orbital moments of grating structure(1.34μ B and 0.24μ B,respectively) decreased 17.3% compared with the corresponding continuous film(1.62μ B and 0.29μ B,respectively).We proposed that the moment decreasing of the patterned grating structure was mainly caused by the etched surface oxidation during the pattern manufacture process.The oxidation ratio of Co element in the patterned grating structure is 14.4% calculated from X-ray absorption spectroscopy(XAS) measurement.Considering the oxidation ratio,we amend the spin and orbital moment of Co and the amended result is basically in accordance with that of continuous film,demonstrating that the difference of the spin and orbital moments between the sub-micron grating unit and the continuous film is really caused by the oxidation.展开更多
基金Project supported by Intelligent Microsystem Center(IMC)Project(2010-0008-276) supported by the National Core Research Center through the National Research Foundation of Korea funded by the Ministry of Education, Science and TechnologyProject(2010) supported by Pusan National University
文摘The etching effect of ammonia (NH3) on the growth of vertically aligned nanotubes/nanofibers (CNTs) was investigated by direct-current plasma enhanced chemical vapor deposition (DC-PECVD). NH3 gas etches Ni catalyst layer to form nanoscale islands while NH3 plasma etches the deposited amorphous carbon. Based on the etching effect of NH3 gas on Ni catalyst, the differences of growing bundles of CNTs and single strand CNTs were discussed; specifically, the amount of optimal NH3 gas etching is different between bundles of CNTs and single strand CNTs. In contrast to the CNT carpet growth, the single strand CNT growth requires shorter etching time (5 min) than large catalytic patterns (10 rain) since nano dots already form catalyst islands for CNT growth. Through removing the plasma pretreatment process, the damage from being exposed at high temperature substrate occurring during the plasma generation time is minimized. High resolution transmission electron microscopy (HTEM) shows fishbone structure of CNTs grown by PECVD.
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supported by the National Natural Science Foundation of China (Grant No. 10274073)the Post-doctoral Research Start-up Funding of Anhui University of Architecture (Grant No. K02553)the Open Project of Building Energy Conservation Institute of Anhui University of Architecture (Grant No. K02592)
文摘Patterned ferromagnetic thin film shows promising applications in ultra-high density magnetic storage,magnetoresistive transducer,magnetic random access memory and many other devices.Since the performance of these devices is closely associated with the magnetic properties of the etched patterns,it is necessary to study the effects of freshly etched surface oxidation on the magnetic properties of the patterned microstructures.In the current work,were carried out an X-ray Magnetic Circular Dichroism(XMCD) study on a 50 nm Co 0.9 Fe 0.1 continuous thin film and a related patterned Co 0.9 Fe 0.1 grating structure etched with a 2 μm period.Based on the sum rules,the spin and orbital moments were calculated for these two samples,respectively.The results indicated that the spin and orbital moments of grating structure(1.34μ B and 0.24μ B,respectively) decreased 17.3% compared with the corresponding continuous film(1.62μ B and 0.29μ B,respectively).We proposed that the moment decreasing of the patterned grating structure was mainly caused by the etched surface oxidation during the pattern manufacture process.The oxidation ratio of Co element in the patterned grating structure is 14.4% calculated from X-ray absorption spectroscopy(XAS) measurement.Considering the oxidation ratio,we amend the spin and orbital moment of Co and the amended result is basically in accordance with that of continuous film,demonstrating that the difference of the spin and orbital moments between the sub-micron grating unit and the continuous film is really caused by the oxidation.