Jie Deng’s research while affiliated with Agency for Science, Technology and Research (A*STAR) and other places

Transferring molecular nanostructures from one surface to another in ultrahigh vacuum (UHV) by mechanical contact might be a possible route to avoid the severe limitations of in situ molecular synthesis on technologically relevant template surfaces. Here, transfer printing in UHV of molecular structures between metal surfaces is investigated by a combination of scanning tunneling microscopy and scanning electron microscopy/energy dispersive x-ray spectroscopy. The authors present the complete procedure of the printing and characterization process. Microstructured Au-coated MoS2 samples exhibiting a periodic pillar structure are used as stamp surfaces with Au(111) single crystals as target surface. Polymers of 1,3,5-tris(4-bromophenyl)benzene molecules and graphene nanoribbons with an armchair edge structure are grown on the pillars of the stamp surface. After bringing the two surfaces in mechanical contact, the transferred material is found on the target while decapping occurs on the stamp surface. Polymer structures are probably buried under the transferred stamp material, and in rare cases, evidence for molecular structures is found in their vicinity. VC 2015 American Vacuum Society. [http://dx.doi.org/10.1116/1.4936886]

Transferring molecular nanostructures from one surface to another in ultrahigh vacuum (UHV) by mechanical contact might be a possible route to avoid the severe limitations of in situ molecular synthesis on technologically relevant template surfaces. Here, transfer printing in UHV of molecular structures between metal surfaces is investigated by a combination of scanning tunneling microscopy and scanning electron microscopy/energy dispersive x-ray spectroscopy. The authors present the complete procedure of the printing and characterization process. Microstructured Au-coated MoS2 samples exhibiting a periodic pillar structure are used as stamp surfaces with Au(111) single crystals as target surface. Polymers of 1,3,5-tris(4-bromophenyl)benzene molecules and graphene nanoribbons with an armchair edge structure are grown on the pillars of the stamp surface. After bringing the two surfaces in mechanical contact, the transferred material is found on the target while decapping occurs on the stamp surface. Polymer structures are probably buried under the transferred stamp material, and in rare cases, evidence for molecular structures is found in their vicinity.

The first experimental demonstration of a controllable rotating molecule gear is presented. A scanning tunneling microscope (STM) is used to construct, manipulate, and observe the rotation of the molecule gear. The appropriate combination of molecule design, molecule manipulation protocol, and surface atomic structure selection leads to the functioning of the molecule gear. Rotation of the molecule gear is done step-by-step and totally under control. The fabrication of solid-state SiO2 nanogears with diameters ranging from 30 nm up to 1 μm and their manipulation using an atomic force microscope tip on a graphite surface is also presented. Ranging in sizes from few tens of nanometers up to submicron diameters, they are going to enable the transmission of mechanical motion from functional mechanical molecule machineries to larger submicron or micron-sized devices through series of solid-state gears and mechanical components compatible with the semiconductor and electronics industry technology.

On a native graphite surface, 15 nm-thick solid-state nanogears are nanofabricated with a 30 nm outer diameter and six teeth. The nanogears are manipulated one at a time by the tip of an atomic force microscope using the sample stage displacements for the manipulation and recording of the corresponding manipulation signals. For step heights below 3.0 nm, nanogears are manipulated up and down native graphite surface step edges. In the absence of a central shaft per nanogear, gearing between nanogears is limited to a few 1/12 turns for six teeth. When the graphite step is higher than 3 nm, a rack-and-pinion mechanism was constructed along the edge with a 90 nm nanogear pinion.

The detailed fabrication and manipulations of solid state nano gears up to 350 nm in diameter is reported. Atomic force microscopy (AFM) and ultra high vacuum (UHV) scanning tunneling microscopy (STM) are used to maneuver the gears. The aim is to bridge the gap between the current solid state gears and the now available nanoscale gears. As in many technology integrations, miniaturization is a way to boost efficiency and an opening to new applications.

A printing technique is proposed for the transfer of metallic nanoislands between two semiconductor surfaces in UHV. For the preparation of the stamp, a systematic study of the growth conditions of small, flat triangular shape Au nanoislands at the top surface of microfabricated MoS2 pillars is presented. Those pillars are organized in a stamping matrix to increase the transfer rate. Up to 10% of Au nanoislands can be transferred to a H-Si�100� surface. The atomic scale quality of the interface between the Au nanoislands and the semiconductor surface is characterized by transmission electron microscopy cross-sectional imaging. This MoS2 stamping technique is extended to other surfaces such as mica, SiO2, and graphite. It permits to handle well shaped Au nanoislands on surfaces where a direct growth of flat nanoislands is not possible. This printing of well defined triangular Au nanoislands offers the unique possibility to construct ultraclean interconnecting nanopad systems by scanning tunneling microscope on atomically clean and electronically suitable substrates, manipulating those nanopads one at a time. The apex of the triangular shaped island is suitable for nanocontact to a surface atomic scale conducting wire.

The manipulation of single metallic nanoislands with a precision better than 0.5 nm on a MoS2 surface is demonstrated. Optimizing the metal growth conditions yields triangular-shaped nanoislands of 30 nm in lateral size and 12 nm in height on the MoS2 surface. The manipulation of a single nanoisland was performed using the tip apex of a scanning tunneling microscope. The feedback loop conditions to achieve this manipulation are discussed. Fully planar four-pad nanostructures were constructed, and the apex of each triangular nanoisland of the nanostructure is pointing toward a central 10�20 nm2 MoS2 working area where the surface atomic cleanliness is preserved.