The present invention provides stretchable, and optionally printable, semiconductors and electronic circuits capable of providing good performance when stretched, compressed, flexed or otherwise deformed. Stretchable semiconductors and electronic circuits of the present invention preferred for some applications are flexible, in addition to being stretchable, and thus are capable of significant elongation, flexing, bending or other deformation along one or more axes. Further, stretchable semiconductors and electronic circuits of the present invention may be adapted to a wide range of device configurations to provide fully flexible electronic and optoelectronic devices.

http://science.sciencemag.org/content/sci/311/5758/208.full.pdf

Stretchable form of single crystal silicon for high performance electronics on rubber substrates

The present invention provides methods, systems and system components for transferring, assembling and integrating features and arrays of features having selected nanosized and/or microsized physical dimensions, shapes and spatial orientations. Methods of the present invention utilize principles of ‘soft adhesion’ to guide the transfer, assembly and/or integration of features, such as printable semiconductor elements or other components of electronic devices. Methods of the present invention are useful for transferring features from a donor substrate to the transfer surface of an elastomeric transfer device and, optionally, from the transfer surface of an elastomeric transfer device to the receiving surface of a receiving substrate. The present methods and systems provide highly efficient, registered transfer of features and arrays of features, such as printable semiconductor element, in a concerted manner that maintains the relative spatial orientations of transferred features.

Pattern Transfer Printing by Kinetic Control of Adhesion to an Elastomeric Stamp

The present invention provides device components geometries and fabrication strategies for enhancing the electronic performance of electronic devices based on thin films of randomly oriented or partially aligned semiconducting nanotubes. In certain aspects, devices and methods of the present invention incorporate a patterned layer of randomly oriented or partially aligned carbon nanotubes, such as one or more interconnected SWNT networks, providing a semiconductor channel exhibiting improved electronic properties relative to conventional nanotubes-based electronic systems.

Medium scale carbon nanotube thin film integrated circuits on flexible plastic substrates

Ultrathin films of single-walled carbon nanotubes (SWNTs) represent an attractive, emerging class of material, with properties that can approach the exceptional electrical, mechanical, and optical characteristics of individual SWNTs, in a format that, unlike isolated tubes, is readily suitable for scalable integration into devices. These features suggest the potential for realistic applications as conducting or semiconducting layers in diverse types of electronic, optoelectronic and sensor systems. This article reviews recent advances in assembly techniques for forming such films, modeling and experimental work that reveals their collective properties, and engineering aspects of implementation in sensors and in electronic devices and circuits with various levels of complexity. A concluding discussion provides some perspectives on possibilities for future work in fundamental and applied aspects.

http://www.ifc.dicp.ac.cn/library/cailiao/pdf1/11.pdf

Ultrathin Films of Single-Walled Carbon Nanotubes for Electronics and Sensors: A Review of Fundamental and Applied Aspects

Carbon Nanotube Thin Films: Fabrication, Properties, and Applications

A printing process for high-resolution transfer of all components for organic electronic devices on plastic substrates has been developed and demonstrated for pentacene (Pn), poly (3-hexylthiophene) and carbon nanotube (CNT) thin-film transistors (TFTs). The nanotransfer printing process allows fabrication of an entire device without exposing any component to incompatible processes and with reduced need for special chemical preparation of transfer or device substrates. Devices on plastic substrates include a Pn TFT with a saturation, field-effect mobility of 0.09cm2(Vs)−1 and on/off ratio approximately 104 and a CNT TFT which exhibits ambipolar behavior and no hysteresis.

Nanotransfer printing of organic and carbon nanotube thin-film transistors on plastic substrates

Photoelectron emission microscopy (PEEM) has been used to investigate simple device structures buried under ultrathin oxides. In particular, we have imaged Au–SiO2 and p-type Si–SiO2 structures and have demonstrated that PEEM is sensitive to these buried structures. Oxide overlayers ranging up to 15.3 nm were grown by systematically varying the exposure time of the structures to a plasma-enhanced chemical-vapor deposition process. The change in image contrast as the oxide thickness increases was used to quantify the inelastic mean-free path of low-energy photoelectrons (∼1 eV) in amorphous silicon dioxide. For Au structures we find that the dominant mean-free path for photoelectrons in the overlying oxide is about 1.18±0.2 nm. Yet, we find a residual observable signal from the buried Au structure through roughly 13 oxide attenuation lengths. The signal attenuation from the Au can be explained by the spread of the photoelectron energies and the energy dependence of the electron–phonon interaction. Similar ...

Photoelectron emission microscopy of ultrathin oxide covered devices

We demonstrate the application of photocurrent modulation spectroscopy in characterizing the performance of organic thin-film transistors. This technique provides a consistent framework to extract the mobility and density of free-carriers from experimental data without relying on assumed models of transport. Applying this technique to pentacene thin-film transistors shows that the mobility increases as ∼Vg1∕3, inconsistent with the prediction of hopping transport. The free-carrier density is approximately 1∕2 of the expected capacitive charge, and the mobility increases monotonically with the free carrier density, consistent with the trap and release model of transport.

Photocurrent probe of field-dependent mobility in organic thin-film transistors

Imaging of devices buried under oxides up to 0.5 μm thick is demonstrated with the photoelectron emission microscope. Specifically, we have observed contrast reversal of entrenched Ti lines, time-dependent oxide charging effects, and visibility of biasing effects when a SiO2 overlayer is present. An internally consistent explanation for all observations is that transport of electrons photoinjected from the buried structures to accessible states in the near-surface region allows for observation of material contrast. The observed contrast reversal is most likely the result of the formation of a TiO2–SiO2 interface, which increases the threshold for photoinjection into the oxide overlayer. Gradual accumulation of charge in trap states in the oxide under continuous UV exposure provides a consistent explanation for the observed time-dependent effects. Contrast effects that accompany biasing of the buried structure are due to the resulting lateral electric field, consistent with known field-effect contrast mech...

Imaging buried structures with photoelectron emission microscopy

We investigate the dependence of the photovoltaic characteristics of organic photocells on the relative concentration of the donor-acceptor molecular complex. The devices were fabricated using a new [MEH-PPV] - co - [phenylene vinylene] blend with C 60 . We find that the morphology and device performance are strongly influenced by the molar fraction (x) of C 60 in the electroactive layer of the device. The best device was obtained with x = 0.6 and manifested V OC = 0.85 V, J SC = 2.65 mA/cm 2 , FF = 0.42, and η P ext = 1%.

M. Breban

Papers

Nanotransfer printing of organic and carbon nanotube thin-film transistors on plastic substrates

Photoelectron emission microscopy of ultrathin oxide covered devices

Photocurrent probe of field-dependent mobility in organic thin-film transistors

Imaging buried structures with photoelectron emission microscopy

Organic photocells based on block copolymer / C60 blends