磁控溅射法制备高性能ZnO薄膜晶体管

研究了磁控溅射法制备的ZnO薄膜晶体管(TFT)。以NH3处理的热生长SiO2作为绝缘层,控制好Ar-O2比等条件溅射合适厚度的ZnO作为器件的有源层。实验表明,与普通条件下热生长的SiO2绝缘层硅片相比,NH3处理的高性能SiO2绝缘层Si片器件的载流子迁移率至少要高1个数量级以上;溅射条件在Ar-O2比25∶1情况下制作的器件性能最好;ZnO薄膜厚度也对ZnO-TFT性能有很大的影响。实验中,采用了4种膜厚,测试表明,其中25nm厚的ZnO薄膜迁移率最大。     

Gate-modulation imaging of organic thin-film transistor arrays: Visualization of distributed mobility and dead pixels

We report on the application of the gate-modulation (GM) imaging technique in rapid and collective inspection of organic thin-film transistor (OTFT) array operations. The method allows visualizing charge carriers accumulated in the OTFT array by time-translational differential image sensing with the use of a charge coupled device (CCD) sensor. The feature makes it possible to visualize the dead pixels, broken channels, or distributed device performance in the OTFT array. We discuss how to correlate the spectroscopic information of GM signal with the device performance and how to use this technique in the collective inspection of OTFT arrays.     

Patchable thin-film strain gauges based on pentacene transistors

We present a patchable thin-film strain gauge for which output current responds sensitively to external strain. For this work, integrated organic thin-film transistors using pentacene as an active component were fabricated on a freestanding polyurethaneacrylate film with high flexibility and adhesive properties providing patchability. The device can be easily mounted onto non-flat surfaces, and the output characteristics show a strong correlation with the structural strain of freestanding polymeric film, which allows the external strain applied to the device to be gauged. In addition, a surface shape can be detected after mounting the device onto a non-flat surface, and the thickness of a complex structure can be inversely calculated using a calibration curve. It is anticipated that these results will be applied to the development of various patchable sensors and thickness measurement systems, which can lead to further applications.     

Up-scaling of the manufacturing of all-inkjet-printed organic thin-film transistors: Device performance and manufacturing yield of transistor arrays

All-inkjet-printed thin-film transistors (TFTs) have been demonstrated in literature using mainly laboratory inkjet equipment, simple one-channel layout and only a low number of manufactured TFT devices. We report on the development and the up-scaling of the manufacturing of all-inkjet-printed TFT arrays using industrial inkjet equipment. The manufacturing of the TFTs was carried out in ambient condition without the need for cleanroom environments or inert atmospheres and at a maximum temperature of 150 °C enabling the use of flexible polymer films as substrate. Arrays of 924 TFTs were manufactured on an area of about DIN A4 (297 × 420 mm²). This allows the consideration of statistics, e.g. to determine the process yield as a function of device design and layout. We present process yields for all-inkjet-printed TTFs up to 82% demonstrating the potential of the developed all-inkjet-printing process.     

One-pot surface modification of poly(ethylene-alt-maleic anhydride) gate insulators for low-voltage DNTT thin-film transistors

This study investigates the one-pot surface modification of poly(ethylene-alt-maleic anhydride) (PEMA) gate insulators crosslinked with 1,5-naphthalenediamine (1,5-NDA) for enhancing the device performance of low-voltage dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) organic thin-film transistors (OTFTs). Surface properties of the PEMA gate insulator could be easily modified by adding poly(maleic anhydride-alt-1-octadecene) (PMAO) to the coating solution. The surface energy of the gate insulator is strongly correlated with the growth of organic semiconductors and the charge carrier transport at the interface between the semiconductor and gate insulator. The results indicate that the device performance of low-voltage DNTT OTFTs can be improved by one-pot surface modification of the PEMA gate insulator.     

All-inkjet-printed low-pass filters with adjustable cutoff frequency consisting of resistors,inductors and transistors for sensor applications

Low-cost and flexible first and second order low-pass filters with adjustable cutoff frequency were designed and printed by inkjet printing technology. The all-inkjet-printed low-pass filters were characterized and an adjustable cutoff frequency feature in form of an inkjet-printed organic thin-film transistors (OTFTs) was added to the filters for application-oriented fine-tuning. The applicability of these small circuits was evaluated by signal filtering for sensor applications. As a result, low-pass filters with an adjustable cutoff frequency ranging from 82 Hz to 740 Hz were obtained, demonstrating their suitability in signal filtering and their promising applicability for tactile sensing characterized by low frequency signals.     

Detachment of compliant films adhered to stiff substrates via van der Waals interactions: role of frictional sliding during peeling

The remarkable ability of some plants and animals to cling strongly to substrates despite relatively weak interfacial bonds has important implications for the development of synthetic adhesives. Here, we examine the origins of large detachment forces using a thin elastomer tape adhered to a glass slide via van der Waals interactions, which serves as a model system for geckos, mussels and ivy. The forces required for peeling of the tape are shown to be a strong function of the angle of peeling, which is a consequence of frictional sliding at the edge of attachment that serves to dissipate energy that would otherwise drive detachment. Experiments and theory demonstrate that proper accounting for frictional sliding leads to an inferred work of adhesion of only approximately 0.5 J m⁻² (defined for purely normal separations) for all load orientations. This starkly contrasts with the interface energies inferred using conventional interface fracture models that assume pure sticking behaviour, which are considerably larger and shown to depend not only on the mode-mixity, but also on the magnitude of the mode-I stress intensity factor. The implications for developing frameworks to predict detachment forces in the presence of interface sliding are briefly discussed.     

32-site microelectrode modified with Pt black for neural recording fabricated with thin-film silicon membrane

Multi-electrode array is an important tool in the study of neural-network,cognition,remembrance,as well as brain-computer-interface,etc.Fork-like 32-site microelectrodes are developed with silicon.By use of integrated circuit technology,the length of the electrodes,the area of the recording sites,as well as the spaces between the sites are closely controlled.SiO2/SiNx/SiO2composite dielectric membrane and Pt black are introduced to improve the characteristics of the electrodes.The whole thickness of the thin-film probe was 21μm.By combining the modifying process with the micro-fabrication method,this kind of silicon based microelectrode satisfies high-density recording and the performance characterization is evaluated by test in vitro and in vivo.     

Structural changes in vapour-assembled n-octylphosphonic acid monolayer with post-deposition annealing: Correlation with bias-induced transistor instability

We report on the link between the structure of n-octylphosphonic acid (C₈PA) monolayer implemented in low-voltage organic thin-film transistors (OTFTs) based on aluminium oxide/C₈PA/pentacene and the kinetics of the transistor bias-induced degradation. Structural changes in the vapour-deposited C₈PA monolayer, studied by Fourier Transform Infrared (FTIR) spectroscopy, are induced by annealing. Changes in the threshold voltage, subthreshold slope, field-effect mobility, and the transistor on-current are measured as functions of the bias stress time and fitted with stretched exponential functions. The presence of C₈PA molecules physisorbed to the monolayer and/or the increased disorder between the aliphatic tails results in substantial degradation of the subthreshold slope and faster reduction in normalized mobility, while slowing the degradation of the threshold voltage. The removal of all physisorbed molecules and improved order between aliphatic tails achieved via optimized post-deposition annealing leads to an improved, microscopically-less-varied interface between C₈PA and pentacene. Consequently, the degradation of the subthreshold slope becomes negligible, the reduction in normalized mobility becomes smaller and the degradation of the threshold voltage dominates. The equilibrium value of the normalized on-current after prolonged bias stress is ∼0.16 regardless of the disorder in C₈PA monolayer, indicating that even though the structure of the monolayer affects the kinetics of the transistor degradation process, the same bias stress condition ultimately leads to the same relative drop in the on-current.     

Electrical characteristics of aluminum-zirconium oxide-barium magnesium fluoride-p silicon MIS capacitors

The Barium Magnesium Fluoride films have been deposited on p-Si wafers at a temperature in the range of 400-450°C in an ion assisted deposition system. X-ray diffraction analysis shows that the films are polycrystalline in nature. The BMF films were encapsulated with an electron beam evaporated Zro2 film of thickness 300°A. The capacitance-voltage (C-V) charactersitics of Aluminum-ZrO2-BMF-p Si MIS capacitors show hysteresis and the direction of the hysterisis correponds to ferroelectric polarization in the BMF film. The shift in threshold voltage was found to depend on bias voltage, ramp rate as well as measurement temperature.