The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
L. E. Brus - One of the best experts on this subject based on the ideXlab platform.
-
reversible Basal Plane hydrogenation of graphene
Nano Letters, 2008Co-Authors: Sunmin Ryu, Melinda Y. Han, Philip Kim, Janina Maultzsch, Tony F Heinz, Michael L Steigerwald, L. E. BrusAbstract:We report the chemical reaction of single-layer graphene with hydrogen atoms, generated in situ by electron-induced dissociation of hydrogen silsesquioxane (HSQ). Hydrogenation, forming sp3 C−H functionality on the Basal Plane of graphene, proceeds at a higher rate for single than for double layers, demonstrating the enhanced chemical reactivity of single sheet graphene. The net H atom sticking probability on single layers at 300 K is at least 0.03, which exceeds that of double layers by at least a factor of 15. Chemisorbed hydrogen atoms, which give rise to a prominent Raman D band, can be detached by thermal annealing at 100∼200 °C. The resulting dehydrogenated graphene is “activated” when photothermally heated it reversibly binds ambient oxygen, leading to hole doping of the graphene. This functionalization of graphene can be exploited to manipulate electronic and charge transport properties of graphene devices.
-
Reversible Basal Plane hydrogenation of graphene
Nano Letters, 2008Co-Authors: Sunmin Ryu, Melinda Y. Han, Philip Kim, Janina Maultzsch, Tony F Heinz, Michael L Steigerwald, L. E. BrusAbstract:We report the chemical reaction of single-layer graphene with hydrogen atoms, generated in situ by electron-induced dissociation of hydrogen silsesquioxane (HSQ). Hydrogenation, forming sp3 C--H functionality on the Basal Plane of graphene, proceeds at a higher rate for single than for double layers, demonstrating the enhanced chemical reactivity of single sheet graphene. The net H atom sticking probability on single layers at 300 K is at least 0.03, which exceeds that of double layers by at least a factor of 15. Chemisorbed hydrogen atoms, which give rise to a prominent Raman D band, can be detached by thermal annealing at 100-200 degrees C. The resulting dehydrogenated graphene is "activated" when photothermally heated it reversibly binds ambient oxygen, leading to hole doping of the graphene. This functionalization of graphene can be exploited to manipulate electronic and charge transport properties of graphene devices.
Marek Skowronski - One of the best experts on this subject based on the ideXlab platform.
-
Direct observation of Basal-Plane to threading-edge dislocation conversion in 4H-SiC epitaxy
Journal of Applied Physics, 2011Co-Authors: Suk Jae Chung, Virginia D. Wheeler, Rachael L. Myers-ward, Charles R. Eddy, D. Kurt Gaskill, Yoosuf N. Picard, Marek SkowronskiAbstract:The propagation behavior of Basal Plane dislocations from off-oriented 4H-SiC substrates into homoepitaxial layers has been investigated using transmission electron microscopy (TEM), secondary electron microscopy (SEM), and chemical etching. Cross-sectional TEM shows that Basal Plane dislocations in the substrate are dissociated into pairs of partial dislocations separated by a stacking fault with a width of about 40 nm. Near the substrate/epilayer interface, where most of the Basal Plane dislocations convert to threading edge dislocations, the two partials constrict before converting. Threading edge segments are inclined by about 20° from the c-axis toward the down-step direction. It is concluded that the critical and limiting step of the dislocation conversion process is constriction of the dissociated partials. Growth surface morphology at the emergence point of the Basal Plane dislocation was imaged using SEM and is thought to play an important role in the constriction.
-
Origin of Basal Plane bending in hexagonal silicon carbide single crystals
Journal of Crystal Growth, 2008Co-Authors: Jae-won Lee, Marek Skowronski, Edward K. Sanchez, Gilyong ChungAbstract:Abstract 4H-SiC crystals grown by the physical vapor transport method were investigated using high-resolution X-ray diffraction, defect selective etching, and transmission electron microscopy. The (0 0 0 8) diffraction peak position shifted about 2.5° along the 3 in crystal diameter indicating the bending of the Basal Plane. Transmission electron microscopy revealed that the Basal Plane bending is due to plastic-deformation-induced Basal Plane dislocations with at least a partial edge character. The dislocations had a non-zero net Burgers vector with the net extra half-Plane pointing toward the seed side of the crystal, and thus, caused the Basal Plane to bend concave toward the growth direction. The plastic deformation is suggested to be due to thermoelastic shear stresses imposed on the crystal during the physical vapor transport (PVT) growth.
-
Basal Plane slip and formation of mixed tilt boundaries in sublimation grown hexagonal polytype silicon carbide single crystals
Journal of Applied Physics, 2002Co-Authors: Marek Skowronski, William M Vetter, Michael DudleyAbstract:Optical microscopy, synchrotron white beam x-ray topography (SWBXT), and high resolution x-ray diffraction (HRXRD) were used to study the distribution of Basal Plane dislocations in bulk 4H silicon carbide crystals grown by the physical vapor transport method. An etch pit array was observed on the silicon face of KOH-etched off-cut wafers. The arrays were aligned parallel to each other and perpendicular to the off-cut direction. The etch pits were oval-shaped, which is characteristic of Basal Plane dislocations. Corresponding array images have been observed by SWBXT. Based on the characteristic distribution, the etch pit arrays are interpreted as the slip traces of high temperature deformation during the growth process. Thermoelastic stress is proposed as the plausible cause of the deformation. In addition, Basal Plane dislocation pileups were found in the proximity of polygonized threading edge dislocation arrays. SWBXT and HRXRD were used to study the misorientation related to such dislocation structure...
Sunmin Ryu - One of the best experts on this subject based on the ideXlab platform.
-
reversible Basal Plane hydrogenation of graphene
Nano Letters, 2008Co-Authors: Sunmin Ryu, Melinda Y. Han, Philip Kim, Janina Maultzsch, Tony F Heinz, Michael L Steigerwald, L. E. BrusAbstract:We report the chemical reaction of single-layer graphene with hydrogen atoms, generated in situ by electron-induced dissociation of hydrogen silsesquioxane (HSQ). Hydrogenation, forming sp3 C−H functionality on the Basal Plane of graphene, proceeds at a higher rate for single than for double layers, demonstrating the enhanced chemical reactivity of single sheet graphene. The net H atom sticking probability on single layers at 300 K is at least 0.03, which exceeds that of double layers by at least a factor of 15. Chemisorbed hydrogen atoms, which give rise to a prominent Raman D band, can be detached by thermal annealing at 100∼200 °C. The resulting dehydrogenated graphene is “activated” when photothermally heated it reversibly binds ambient oxygen, leading to hole doping of the graphene. This functionalization of graphene can be exploited to manipulate electronic and charge transport properties of graphene devices.
-
Reversible Basal Plane hydrogenation of graphene
Nano Letters, 2008Co-Authors: Sunmin Ryu, Melinda Y. Han, Philip Kim, Janina Maultzsch, Tony F Heinz, Michael L Steigerwald, L. E. BrusAbstract:We report the chemical reaction of single-layer graphene with hydrogen atoms, generated in situ by electron-induced dissociation of hydrogen silsesquioxane (HSQ). Hydrogenation, forming sp3 C--H functionality on the Basal Plane of graphene, proceeds at a higher rate for single than for double layers, demonstrating the enhanced chemical reactivity of single sheet graphene. The net H atom sticking probability on single layers at 300 K is at least 0.03, which exceeds that of double layers by at least a factor of 15. Chemisorbed hydrogen atoms, which give rise to a prominent Raman D band, can be detached by thermal annealing at 100-200 degrees C. The resulting dehydrogenated graphene is "activated" when photothermally heated it reversibly binds ambient oxygen, leading to hole doping of the graphene. This functionalization of graphene can be exploited to manipulate electronic and charge transport properties of graphene devices.
Ruiqi Wang - One of the best experts on this subject based on the ideXlab platform.
-
Basal Plane bending of 4H-SiC single crystals grown by sublimation method with different seed attachment methods
CrystEngComm, 2018Co-Authors: Xianglong Yang, Xiao Bo Hu, Xiu Fang Chen, Xian Gang Xu, Jinying Yu, Xianglai Yang, Yingxin Song, Yan Peng, Ruiqi WangAbstract:Basal Plane bending of 4H-SiC single crystals grown using the sublimation method on an open or closed backside seed was measured using high-resolution X-ray diffractometry. In order to allow full information to be obtained about the complexity of Basal Plane bending, line scans of the 0004 reflection rocking curves were carried out on the (0001) Si face along the , , , , and directions. The measurement results revealed the seed attachment had a pronounced effect on the Basal Plane bending behaviors. The single crystals grown on a closed backside seed exhibit strong Basal Plane bending which is rotationally symmetric and concave towards the growth direction. However, the single crystals grown on an open backside seed show much weaker Basal Plane bending. The Basal Plane bending inheritance of 4H-SiC single crystals grown by sublimation with two different seed attachment methods was studied. Moreover, the Basal Plane bending characteristics of 4H-SiC crystals grown on an open backside seed with apparent axisymmetric Basal Plane bending were investigated. Molten KOH etching was carried out to correlate the Basal Plane bending with the distribution of structural defects to understand the Basal Plane bending mechanism. Finally, the effect of macroscopic shear stress resulting from the difference in the thermal expansion coefficient between the silicon carbide (SiC) seed and graphite holder and the induced structural defects on the Basal Plane bending of 4H-SiC single crystals was explored.
Robert A. W. Dryfe - One of the best experts on this subject based on the ideXlab platform.
-
electrochemistry of the Basal Plane versus edge Plane of graphite revisited
Journal of Physical Chemistry C, 2019Co-Authors: Matej Velicky, Peter S. Toth, Colin R. Woods, Kostya S. Novoselov, Robert A. W. DryfeAbstract:The electrochemical activity of the Basal Plane and edge Plane of graphite has long been a subject of an extensive debate. While significant advances have been made, several gaps still exist in our...
-
Electrochemistry of the Basal Plane versus Edge Plane of Graphite Revisited
The Journal of Physical Chemistry, 2019Co-Authors: Matej Velicky, Peter S. Toth, Colin R. Woods, Kostya S. Novoselov, Robert A. W. DryfeAbstract:The electrochemical activity of the Basal Plane and edge Plane of graphite has long been a subject of an extensive debate. While significant advances have been made, several gaps still exist in our understanding of this issue, namely, the relative differences in the electrochemical activity of the perfect Basal Plane and perfect edge Plane and the dependence of measurable electrochemical quantities on the edge/defect density of the Basal Plane. In this work, we employ a microdroplet electrochemical cell technique and atomic force microscopy to measure localized electrochemical properties of the graphitic surface with known edge coverage. The electron transfer rate, capacitance, and density of electronic states of the perfect Basal Plane and perfect edge Plane are estimated, and a qualitative model is proposed for the dependence of the electrochemical quantities on the defect density of the Basal Plane.
