Hyun-Seok Kim

A nanomechanical computer?exploring new avenues of computing

We propose a fully mechanical computer based on nano-electromechanical elements. Our aim is to combine this classical approach with modern nanotechnology to build a nanomechanical computer (NMC) based on nanomechanical transistors. The main motivation behind constructing such a computer is threefold: (i) mechanical elements are more robust to electromagnetic shocks than current dynamic random access memory (DRAM) based purely on complimentary metal oxide semiconductor (CMOS) technology, (ii) the power dissipated can be orders of magnitude below CMOS and (iii) the operating temperature of such an NMC can be an order of magnitude above that of conventional CMOS.

Laser drilling of nano-pores in sandwiched thin glass membranes

We report on a novel method of using an excimer laser to drill ultra-small pores in borosilicate glass membranes. By introducing a thin layer of liquid between sandwiches of two glass slides, we can shrink the pore size and smoothen the surface on the exit side. We are able to push the minimal exit pore diameter down to 90 nm, well below the laser wavelength of 193 nm. This is achieved with substrates over 150 microm thick. Compared to other methods, this technique is fast, inexpensive, and produces high quality smooth pores.

Nanopillar arrays on semiconductor membranes as electron emission amplifiers

A new transmission-type electron multiplier was fabricated from silicon-on-insulator (SOI) material by integrating an array of one-dimensional (1D) silicon nanopillars onto a two-dimensional (2D) silicon membrane. Primary electrons are injected into the nanopillar-membrane (NPM) system from the flat surface of the membrane, while electron emission from the nanopillars is probed by an anode. The secondary electron yield (SEY) from the nanopillars in the current device is found to be about 1.8 times that of the plain silicon membrane. This gain in electron number is slightly enhanced by the electric field applied from the anode. Further optimization of the dimensions of the NPM and an application of field emission promise an even higher gain for detector applications and allow for probing of electronic/mechanical excitations in an NPM system stimulated by incident particles or radiation.

Subthreshold field emission from thin silicon membranes

We report on strongly enhanced electron multiplication in thin silicon membranes. The device is configured as a transmission-type membrane for electron multiplication. A subthreshold electric field applied on the emission side of the membrane enhances the number of electrons emitted by two orders of magnitude. This enhancement stems from field emitted electrons stimulated by the incident particles, which suggests that stacks of silicon membranes can form ultrasensitive electron multipliers.

Direct observation of sub-threshold field emission from silicon nanomembranes

Excited by an energetic electron beam, field enhanced electron emission from a silicon nanomembrane is examined by using a local current probe. The experiments reveal clear transitions from conventional secondary electron emission (SEE) to sub-threshold field electron emission (SFE) and then to conventional field electron emission (FEE). An electron yield of more than 104 is obtained and a model of sub-threshold emission is verified. Ultra sensitive charge/particle detectors could be realized by implementing sub-threshold field emission in nano scale structures, where electron excitations occur within the screen depth of surface electric field.

Marshmallowing of nanopillar arrays by field emission

We fabricated nanoscale field electron emitters formed by highly-doped silicon nanopillars on a silicon membrane. Electron-beam induced deposition of carbon-based contaminants is employed as a probe of the spatial activity of electron emission from the nanopillars. In stark contrast to the general assumption that field emission only occurs at the tips of nanoscale emitters, we found strong emission from the sidewalls of the nanopillars. This is revealed by the deposition of carbon contaminants on these sidewalls, so that the nanopillars finally resemble marshmallows. We conclude that field emission from nanostructured surfaces is more intricate than previously expected.