Showing papers by "Jong Hyun Ahn published in 2008"

Stretchable and foldable silicon integrated circuits.

Abstract: We have developed a simple approach to high-performance, stretchable, and foldable integrated circuits. The systems integrate inorganic electronic materials, including aligned arrays of nanoribbons of single crystalline silicon, with ultrathin plastic and elastomeric substrates. The designs combine multilayer neutral mechanical plane layouts and "wavy" structural configurations in silicon complementary logic gates, ring oscillators, and differential amplifiers. We performed three-dimensional analytical and computational modeling of the mechanics and the electronic behaviors of these integrated circuits. Collectively, the results represent routes to devices, such as personal health monitors and other biomedical devices, that require extreme mechanical deformations during installation/use and electronic properties approaching those of conventional systems built on brittle semiconductor wafers.

Theoretical and Experimental Studies of Bending of Inorganic Electronic Materials on Plastic Substrates

Abstract: This paper describes materials and mechanics aspects of bending in systems consisting of ribbons and bars of single crystalline silicon supported by sheets of plastic. The combined experimental and theoretical results provide an understanding for the essential behaviors and for mechanisms associated with layouts that achieve maximum bendability. Examples of highly bendable silicon devices on plastic illustrate some of these concepts. Although the studies presented here focus on ribbons and bars of silicon, the same basic considerations apply to other implementations of inorganic materials on plastic substrates, ranging from amorphous or polycrystalline thin films, to collections of nanowires and nanoparticles. The contents are, as a result, relevant to the growing community of researchers interested in the use of inorganic materials in flexible electronics.

Semiconductor Wires and Ribbons for High- Performance Flexible Electronics

Abstract: This article reviews the properties, fabrication and assembly of inorganic semiconductor materials that can be used as active building blocks to form high-performance transistors and circuits for flexible and bendable large-area electronics. Obtaining high performance on low temperature polymeric substrates represents a technical challenge for macroelectronics. Therefore, the fabrication of high quality inorganic materials in the form of wires, ribbons, membranes, sheets, and bars formed by bottom-up and top-down approaches, and the assembly strategies used to deposit these thin films onto plastic substrates will be emphasized. Substantial progress has been made in creating inorganic semiconducting materials that are stretchable and bendable, and the description of the mechanics of these form factors will be presented, including circuits in three-dimensional layouts. Finally, future directions and promising areas of research will be described.

Complementary Logic Gates and Ring Oscillators on Plastic Substrates by Use of Printed Ribbons of Single-Crystalline Silicon

Abstract: CMOS inverters and three-stage ring oscillators were formed on flexible plastic substrates by transfer printing of p-type and n-type single crystalline ribbons of silicon. The gain and the sum of high and low noise margins of the inverters were as high as ~150 and 4.5 V at supply voltages of 5 V, respectively. The frequencies of the ring oscillators reached 2.6 MHz at supply voltages of 10 V. These results, as obtained with devices that have relatively large critical dimensions (i.e., channel lengths in the several micrometer range), taken together with good mechanical bendability, suggest promise for the use of this type of technology for flexible electronic systems.

Complementary metal oxide silicon integrated circuits incorporating monolithically integrated stretchable wavy interconnects

Abstract: Stretchable complementary metal oxide silicon circuits consisting of ultrathin active devices mechanically and electrically connected by narrow metal lines and polymer bridging structures are presented. This layout—together with designs that locate the neutral mechanical plane near the critical circuit layers—yields strain independent electrical performance and realistic paths to circuit integration. A typical implementation reduces the strain in the silicon to less than ∼0.04% for applied strains of ∼10%. Mechanical and electrical modeling and experimental characterization reveal the underlying physics of these systems.

Defect Tolerance and Nanomechanics in Transistors that Use Semiconductor Nanomaterials and Ultrathin Dielectrics

Abstract: This paper describes experimental and theoretical studies of the mechanics of free-standing nanoribbons and membranes of single-crystalline silicon transfer printed onto patterned dielectric layers. The results show that analytical descriptions of the mechanics agree well with experimental data, and they explicitly reveal how the geometry of dielectric layers (i.e., the width and depth of the features of relief) and the silicon (i.e., the thickness and widths of the ribbons) affect mechanical bowing (i.e., ‘‘sagging’’) in the suspended regions of the silicon. This system is of practical importance in the use of semiconductor nanomaterials for electronic devices, because incomplete sagging near defects in gate dielectrics provides a level of robustness against electrical shorting in those regions which exceeds that associated with conventional deposition techniques for thin films. Fieldeffect transistors formedusingsilicon nanoribbonstransferred onto arangeofultrathingate dielectrics, includingpatterned epoxy, organic self-assembled monolayers, and HfO2, demonstrate these concepts.

Semiconductor Wires and Ribbons for High‐Performance Flexible Electronics

Abstract: This article reviews the properties, fabrication and assembly of inorganic semiconductor materials that can be used as active building blocks to form high-performance transistors and circuits for flexible and bendable large-area electronics. Obtaining high performance on low temperature polymeric substrates represents a technical challenge for macroelectronics. Therefore, the fabrication of high quality inorganic materials in the form of wires, ribbons, membranes, sheets, and bars formed by bottom-up and top-down approaches, and the assembly strategies used to deposit these thin films onto plastic substrates will be emphasized. Substantial progress has been made in creating inorganic semiconducting materials that are stretchable and bendable, and the description of the mechanics of these form factors will be presented, including circuits in three-dimensional layouts. Finally, future directions and promising areas of research will be described.

Semiconductor-based optical system and method of making the same

Abstract: The present invention provides 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. Optical systems of the present invention include, however, devices and device arrays provided on conventional rigid or semi-rigid substrates, in addition to devices and device arrays provided on flexible, shapeable and/or stretchable substrates.