In this letter, we report the effects of electromechanical and mechanical strain on amorphous ZIO thin-film transistors (TFTs), deformed on cylindrical surfaces of varying radii for varying time ...spans. The TFTs were fabricated on island structures on polyethylene napthalate and subjected to both tensile and compressive stress, parallel and perpendicular to the conducting channel length. Mobility increased while the subthreshold slope decreased with tensile stress, and reverse changes were observed with compressive stress, both being parallel to the channel length. Almost no changes were observed for perpendicular stress, within experimental errors. The magnitude of change also depended on the time duration of the strain. None of the changes were catastrophic to cause complete failure of the devices.
The influence of the mechanical bending, rolling and crimping of flexible screen-printed electrodes upon their electrical properties and electrochemical behavior has been elucidated. Three different ...flexible plastic substrates, Mylar, polyethylene naphthalate (PEN), and Kapton, have been tested in connection to the printing of graphite ink working electrodes. Our data indicate that flexible printed electrodes can be bent to extremely small radii of curvature and still function well, despite a marginal increase the electrical resistance. Below critical radii of curvature of ∼8
mm, full recovery of the electrical resistance occurs upon strain release. The electrochemical response is maintained for sub-mm bending radii and a 180° pinch of the electrode does not lead to device failure. The electrodes appear to be resistant to repeated bending. Such capabilities are demonstrated using model compounds, including ferrocyanide, trinitrotoluene (TNT) and nitronaphthalene (NN). These printed electrodes hold great promise for widespread applications requiring flexible, yet robust non-planar sensing devices.
This paper presents a low-noise and low-current autozeroed (AZ) dual-stage active-pixel-sensor circuit with a noise figure of 830 input-referred rms electrons and compares its performance with the ...conventional pixel with a figure of 1950 electrons. Through the analysis, we show how the dual stage can increase the photoinduced signal transconductance gain while keeping the relative output-referred noise low by using lower bias currents. From the analysis and verified-via-noise measurements, we report a 55% reduction in the input-referred noise using the optimized readout. The new design performs reset autozeroing, which stabilizes the gain every reset period. Using a subthreshold-mode a-Si:H TFT photodetector, the designed AZ dual stage provided the maximum gain with transient light. The dual stage is also less sensitive to electrical degradation induced by stressing but increases the overall pixel size.
Integrated source drivers for a 4'' Quarter Video Graphics Array (QVGA) electrophoretic display have been developed using amorphous silicon TFTs on flexible stainless steel substrate. The current ...design reduces the number of column interconnects to the display by more than 3times compared to a display with external drivers. This integration reduces cost and improves reliability
► This paper studies the impact of drain bias stress, under fixed gate bias in a-IZO TFTs. ► The change in
V
T
is more for higher drain bias. ► Both subthreshold slope and transfer characteristics ...change but recover when left unstressed. ► The degradation follows logarithmic model, associated with charge trapping. ► All observations point to charge trapping as degradation mechanism.
Drain bias stress effects on amorphous Zinc Indium Oxide (a-ZIO) Thin Film Transistors (TFTs) are important in flexible electronic systems. The drain bias impacts the overall threshold voltage (
V
th
) shift more so in the saturation stress mode than in the linear stress mode. Localization of degradation region in channel results in asymmetry in post stressed drain current in forward and reverse operations. This brief studies the impact of drain bias on
V
th
degradation, and also the effect on post stressed forward and reverse currents in a-ZIO TFTs, under both positive and negative gate bias stress in different regions of operation. Based on the measured results, an empirical expression incorporating drain bias effect on
V
th
degradation is derived. Also the measured results point to charge trapping in the insulator–semiconductor interface as the dominant degradation mechanism.
In this letter, we present the dc characteristics, stability, and low-frequency noise (LFN) measurements, for n-type indium arsenide nanowire (NW) parallel-array thin-film transistors (TFTs) with a ...global back gate. These devices perform with mobilities ranging from 200-1200 cm 2 V -1 s -1 and produce a threshold voltage shift less than 0.25 V after 10 000 s of stress. The resulting LFN measurements indicate that the 1/ f noise can be modeled by the number fluctuation model, at low drain currents, which can provide an essential guideline for the device design considerations of NW TFTs.
This paper presents a new flexible electronics assembly technique that combines individual digital X-ray detectors to create a much larger composite digital X-ray detector. The new assembly technique ...uses multiple flexible digital X-ray detectors manufactured on a thin, transparent, and flexible plastic substrate, which are overlapped to create the larger composite X-ray detector. The assembly technique, illustrated in a mechanical mockup, is optically seamless, and has the ability to scale up to extremely large X-ray imaging arrays. Feasibility and preliminary imaging performance were demonstrated by tiling several 16 × 16 pixel resolution prototype flexible X-ray detector test structures. Optical losses under typical digital radiography conditions were also measured by overlapping a plastic substrate flexible X-ray detector onto a commercial glass substrate digital X-ray imaging array. Approximately 5% signal loss was observed in the transparent plastic overlap region, and the seam edge imaging artifact was demonstrated to be correctable using commercial gain calibration. A key medical imaging application for this technology is single-exposure, low-dose, and full-body digital radiography.
Hydrogen plays a critical role in the passivation of dangling bonds in hydrogenated amorphous silicon (a-Si:H) to enable acceptable semiconducting characteristics during operation in devices. Low ...temperature processing enables fabrication of high performance transistors on flexible substrates such as plastic or stainless steel foils, but also leads to a decrease in the stability of the electronic performance. Generation of defects at the a-Si:H/insulator (hydrogenated silicon nitride, SiN:H) during electrical use due to localized heating will lead to decreased performance unless the dangling bonds are passivated in-situ by residual hydrogen. For this reason, the distribution of hydrogen within a-Si:H may be critical to understanding their aging phenomena. Here the distribution of hydrogen within both a-Si:H and SiN:H layers is probed with sub-nanometer resolution using neutron reflectivity. The hydrogen concentration within the bulk of the a-Si:H (11
±
2 at.%) and SiN:H (18
±
3 at.%) agree well with previous reports, but the increased resolution of the neutron measurement is able to identify an approximate three fold increase in the concentration within 2
nm of the semiconductor–insulator interface. This enhanced hydrogen content may act in the short-term as a sink to passivate any dangling bonds formed during operation.
► Neutron reflectivity non-destructively quantifies the hydrogen content in amorphous silicon and silicon nitride. ► 3 fold excess of hydrogen within 2
nm of amorphous silicon/silicon nitride determined from neutron reflectivity. ► Spectroscopic ellipsometry cannot detect this thin layer of excess hydrogen.
Analog comparator arrays fabricated on a bulk CMOS 130-nm are measured to quantify input-referred offsets due to transistor variation and kickback noise. Comparators using RHBD edgeless and ...conventional two-edge transistors are compared to determine the impact on the circuit behavior. Both random variation and kickback noise are slightly larger than for an equivalent design using two-edge transistors. The input-referred offsets are shown to be completely systematic.
The change in electrical characteristics of a-Si:H thin-film transistors (TFTs) was determined in the presence of electrical gate bias stress, gamma radiation, and both simultaneously, simulating the ...harsh environment of space. Multiple TFTs were tested under each condition, and the current-voltage characteristics were measured. The results show the gate bias stress increasing the threshold voltage ( VT ) with power law time dependence while the gamma irradiation decreases threshold voltage for all working transistors. When both the irradiation and gate bias stress were applied simultaneously, the VT initially increased with electrical stress and then decreased as the gamma radiation dominated. Changes in effective mobility were also extracted and detailed analysis of the current-voltage characteristics indicated that the gamma radiation creates interface traps and electron-hole pairs whereas the gate stress produces defect states in the amorphous silicon.
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