Thin film transistors of nanocrystalline silicon (nc-Si:H) are made in the staggered topgate, bottom-source/drain geometry. To achieve both high carrier mobility and low off current, the nc-Si:H channel material must be kept thin but comprise a contiguous 10-nm thick crystalline layer at its top. We study this electrically most interesting top layer of the nc-Si:H channel film by AFM and SEM. Introducing an nc-Si:H seed layer underneath the TFT promotes the structural evolution of the nc-Si:H channel layer and raises the electron field effect mobility up to 40 cm2V-1s-1.

Amorphous silicon nitride (a-SiNx) is widely used as the gate dielectric and passivation layer in a-Si:H based electronics. For devices on plastic substrates deposited at low temperature, the a-SiNx quality seems to determine the device performance. This paper investigates the effects of hydrogen dilution, helium dilution, ammonia-silane gas flow ratio, and RF power on the properties of PECVD silicon nitrides deposited in large-area parallel-plate reactors at substrate temperatures of 75°C. The chemical composition and bonding of the SiNx:H films was studied using FTIR spectroscopy. The physical properties were investigated, and the density, growth rate, and compressive stress of the films were determined. The electrical properties such as leakage current, breakdown, stability, trap density, and dielectric constant of the films were characterized by I-V and C-V measurements of metal-insulator semiconductor (MIS) structures. Analysis of Variance (ANOVA) was performed on the results, and the deposition conditions for the optimal film properties were determined. The optimum film had SiNx:H stoichiometry of x=1.56 with hydrogen concentrations of 17 at.%, and exhibited compressive stress of -220 MPa. The film displayed good stability under electrical stress with ohmic leakage of Rleak ∼1016 Ωcm. Strong relationships between the film properties and deposition conditions were observed, and are discussed within the paper. A-Si:H bottom gate TFTs were fabricated using the optimized nitrides for gate dielectrics and passivation layers, and the influence of a-SiNx on TFT performance is discussed.

For applications in polymer electronics, suitable passivation coatings are searched for. Inorganic-organic hybrid polymers (ORMOCER®.s) have proven to be tunable in a wide range with respect to their physical properties. Their synthesis can be controlled such that the resulting materials show very low water vapor transition rates (WVTR) which is one of the most important key properties for passivation applications. Besides, ORMOCER®.s can be patterned by UV lithography due to their organic functional groups thus yielding the possibility of selectively passivate electronic circuits. Typical WVTR values which have been achieved so far for individual thin-film layers range between approximately 1 and 5 g/m2d (calculated for 100 μm layer thickness). The passivation properties will be discussed with respect to variations of the inorganic content and to the network formed upon processing.

This paper presents the first demonstration of amorphous silicon (a-Si:H) thin film transistor (TFT) circuit integration on plastic substrates. The circuits compensate for material shortcomings such as metastable threshold voltage (VT) shift and high contact resistance, to supply stable and predictable currents to drive organic light emitting diode (OLED) displays on plastic. Various drive circuits were fabricated and tested. The simplest pixel driver circuit possible is the two TFT voltage-programmed circuit, which is very susceptible to any shift in VT of the drive TFT. To overcome this problem, we have developed current-programmed pixel circuits based on the current mirror circuit family, which include the simple and cascode current mirrors. The OLED current in these circuits is virtually independent of any VT shift or mobility variation in the drive TFT. Results show that the circuits provide higher linearity and dynamic range than currently available pixel circuits while minimizing the pixel area.

Capacitors, resistors and inductors are surface mounted components on circuit boards, which occupy up to 70% of the circuit board area. For selected applications, these passives are packaged inside green ceramic tape substrates and sintered at temperatures over 700°C in a co-fired process. These high temperature processes are incompatible with organic substrates, and low temperature processes are needed if passives are to be embedded into organic substrates. A new high permeability dual-phase Nickel Zinc Ferrite (DP NZF) core fabricated using a low temperature sol-gel route was developed for use in embedded inductors in organic substrates. Crystalline NZF powder was added to the sol-gel precursor of NZF. The solution was deposited onto the substrates as thin films and heat-treated at different temperatures. The changes in the microstructures were characterized using XRD and SEM. Results showed that addition of NZF powder induced low temperature transformation of the sol-gel NZF phase to high permeability phase at 250°C, which is approximately 350°C lower than transformation temperature for pure NZF sol gel films. Electrical measurements of DP NZF cored two-layered spiral inductors indicated that the inductance increased by three times compared to inductors without the DP NZF cores. From microstructural observations, the increase is correlated with the changes in microstructural connectivity of the powder phase.

In the study presented here, we successfully demonstrated that high quality ITO films could be obtained on plastic substrates using Excimer laser crystallization. ITO films were first deposited at 10 °C on PEN substrates by DC magnetron sputtering, and then irradiated using a homogenized pulsed XeCl excimer laser beam (308 nm, 35 ns pulse duration) in a vacuum chamber. It was possible to reliably attain Type I ITO films with sheet resistances down to 35 Ω/΢, combined with 80 % optical transmittance in visible range. Well defined 2 μm lines could be obtained using simple HCl etchant at room temperature. We also developed Type II ITO films with a sheet resistance of 15 Ω/΢ and an optical transmittance of 80 % by means of laser annealing on plastic substrates, although these materials were found inferior to Type I in etching properties.

Nanoparticles are known to melt at temperatures well below the bulk melting point. This behavior is being exploited for the recrystallization of Germanium to form large-grain semiconductor thin films on flexible and low temperature substrates. The melting of Ge nanoparticles as a function of size was investigated using the ab-initio Harris functional method of density functional theory (DFT).

The DFT code was initially evaluated for its ability to predict the bulk properties of crystalline Ge. A conjugate gradient method was employed for minimizing the multiphase atomic positional parameters of the diamond, BC8 and ST12 structures. The computed lattice constants, bulk moduli, and internal atomic positional parameters were found to agree well with other calculations and with reported experimental results.

A constant temperature Nose-Hoover thermostat was added to the DFT code in order to compute thermal properties via molecular dynamics. The simulations were tested on a 13-atom Ge cluster, which was found to melt at 820 K. Further heating resulted in the cluster breaking up into two smaller clusters, which remained stable up to 1300K.

Polyester films are well-known substrates for a wide range of electronic applications. This contribution will describe new developments in polyester film substrates for OLED displays.

We report a simple and mild fabrication of flexible organic field-effect transistors (OFETs) by an electrode-peeling transfer method. Firstly, fine patterns of source-drain metal electrodes were formed on a solid substrate, where a micro-patterning process such as photolithography is applicable. An organic dielectric layer (poly-chloro-p-xylylene) was deposited by a chemical vapor deposition. Then patterned gate electrode was deposited using a shadow mask. On the top surface of the gate electrode, another adhesive flexible substrate was fixed and the stack of the flexible substrate/gate electrode /dielectric layer /source-drain electrode was peeled away from the solid substrate. The peeling-transfer was completed with a help of a self-assembled monolayer of n-decyl mercaptan as a connecting buffer layer between the gold electrodes and the dielectric layer. Then an organic semiconductor material was deposited on the fresh peeled-off surface on the flexible substrate. When pentacene was used as the semiconductor material, the OFETs exhibited a hole mobility of 0.1 cm2/Vs and a current on/off ratio of 105.

In recent years, there has been tremendous interest in all-printed electronics as a means of achieving ultra-low-cost electronic circuits with uses in displays and disposable electronics applications such as RFID tags. While there have been a few demonstrations of printed organic transistors to date, there has been little work on the associated passive component and interconnection technologies required to enable the development of all-printed RFID circuits. In particular, low-resistance conductors are crucial to achieve the high-Q inductors necessary for RFID. Here, we demonstrate inkjetted nanoparticle-Au conductors on plastic with sheet resistances as low as 0.03 ohms/square. We describe the optimization of the jetting parameters, and their impact on final film morphology and electrical properties. We also demonstrate a bridging technology based on an inkjetted polyimide interlevel dielectric. Using this process, we demonstrate multilevel interconnect and passive component structures including conductor patterns, crossover bridges, and tapped planar spiral inductors. Together, these represent an important step towards the realization of all-printed RFID.

The reduced melting point and high solubility of inorganic nanoparticles have been shown to be useful in the low-temperature solution-based fabrication of semiconductor devices. These inks have been patterned using various techniques to form inorganic logic elements, multi-layer structures, and MEMS. Here we report a new technique known as offset liquid embossing that is used to print the nanoparticle inks. Structures created include multiple layers of gold and spin-on-glass printed without the need for etching or planarization, and 100 nm resolution.

New applications in the electronics market ranging from foldable displays in mobile phones to wearable displays in clothes generate a high demand for flexible materials especially for substrates. The upcoming OLED technology shows some advantages in comparison with conventional LCDs and enables real flexible or shaped displays. Moreover, the wearable displays have a barely need for flexible electronic circuits. At a first glance polymer foils are the materials of choice for flexible substrates and for electronic circuits but in general they suffer from thermal instability as well as from high permeation rates for gases and water and hence chemical stability of critical materials such as LC's or low work function materials. In contrast, even ultra thin glass sheets have excellent barrier properties and show sufficient bending properties if they are thinner than 100μm.

Flexible glass substrates down to a thickness of 50μm have been developed. The deposition of an organic coating helps to overcome significantly the lack of mechanical stability. Therefore, our flexible glass substrates can be used in conventional display manufacturing processes which include several thin film process steps. Moreover, they are suited for production of flexible PCB's.