Showing papers by "Jong Hyun Ahn published in 2007"

Optical systems fabricated by printing-based assembly

Abstract: Provided are optical devices and systems fabricated, at least in part, via printing-based assembly and integration of device components. In specific embodiments the present invention provides light emitting systems, light collecting systems, light sensing systems and photovoltaic systems comprising printable semiconductor elements, including large area, high performance macroelectronic devices. Optical systems of the present invention comprise semiconductor elements assembled, organized and/or integrated with other device components via printing techniques that exhibit performance characteristics and functionality comparable to single crystalline semiconductor based devices fabricated using conventional high temperature processing methods. Optical systems of the present invention have device geometries and configurations, such as form factors, component densities, and component positions, accessed by printing that provide a range of useful device functionalities. Optical systems of the present invention include devices and device arrays exhibiting a range of useful physical and mechanical properties including flexibility, shapeability, conformability and stretchablity.

Bendable integrated circuits on plastic substrates by use of printed ribbons of single-crystalline silicon

Abstract: This letter presents studies of several simple integrated circuits—n-channel metal-oxide semiconductor inverters, five-stage ring oscillators, and differential amplifiers—formed on thin, bendable plastic substrates with printed ribbons of ultrathin single-crystalline silicon as the semiconductor. The inverters exhibit gains as high as 2.5, the ring oscillators operate with oscillation frequencies between 8 and 9MHz at low supply voltages (∼4V), and the differential amplifiers show good performance and voltage gains of 1.3 for 500mV input signals. The responses of these systems to bending-induced strains show that relatively moderate changes of individual transistors can be significant for the operation of circuits that incorporate many transistors.

Unsupervised morphing by conjugate image processing

Abstract: Unsupervised image morphing is a very challenging task in machine learning, whereas it is relatively easy and common for the human brain. Even a simple deformation of an object such as a translation or scaling operation follows a complex curved trace in a high-dimensional image space. The learning of such a complex curved manifold needs human assistance or sufficiently dense intermediate data points. Presented is a novel transformation framework with which a curved manifold describing the deformation of images turns into a simple linear structure in the transformed space. Therefore, image morphing can be achieved by simple linear superposition using the conjugate image representation.

Cold plasma generation by optical field ionization with hydrogen and helium gas mixture

Abstract: To generate plasmas with low average electron energy, the optical field ionized plasmas with helium and hydrogen gas mixture was studied. To measure the average electron energy, the line intensity ratio was measured experimentally and calculated using an atomic kinetic model. The measured line intensity ratio indicates that the average electron energy is 3 eV for the case of 5 % helium and 95 % hydrogen gas mixture.