A large mechanical sensitivity can be achieved by a mechanically tunable quantum tunneling barrier. The tunneling resistance across the nanometer-sized gap can be changed by several orders of magnitude through a sub-angstrom-scale displacement. Here, we demonstrate the performance of a strain sensor formed from pre-stretched Platinum (Pt) on PDMS, where perturbation of the thickness of the nanogap cracks due to strain change the resistance of the device. A gauge factor >500 is realized in a device that is mechanically stabilized by self-assembled monolayer (SAM). Then, we extend the application of the nanogap based strain sensor to temperature and infrared detection. Fabricated proof-of-concept metal/SAM/metal suspended bolometers yield a temperature coefficient of resistance (TCR) between -0.006 K-1 and - 0.085 K-1, and theoretical predictions show that with further optimization the TCRs could be improve to as much as -2.7 K-1, which is more than one order of magnitude better than the state-of-the-art VOx bolometers. Furthermore, this work quantifies the 50 Hz to 10 kHz noise performance of suspended metal/nanogap/metal bolometers and compares the noise spectrum of devices with and without SAM, as well as 10 nm Pt channel vs. 30 nm Pt channel devices. Finally, early stage 830 nm optical measurements show that the device sensitivity of a 10nm Pt / air nanogap / 10 nm Pt peaks at low bias (< 1V, <20 pA) and that the 3dB point of the sensor extends past 10 kHz. The experimental results of this work suggest that nanogap-based sensor architectures exhibit a high sensitivity and may also enable fast response time detectors.
We demonstrate efficient solar cells based on an active layer of methylammonium lead iodide (MAPbI3) co-deposited via vapor transport deposition (VTD). In VTD organic and metal-halide precursor vapors are transported by carrier gas to a cooled substrate where film formation occurs. Our system design enables control over a range of process parameters allowing co-deposition and composition tuning of the final perovskite film. The impact of VTD processing conditions on film composition and solar cell performance will be discussed, with emphasis on tuning the lead iodide content in MAPbI3 films to realize power conversion efficiencies >10%.
We demonstrate that attenuated luminescence and lasing in optically excited organic thin films is a sensitive probe to vapours of explosives, such as trinitrotoluene (TNT). The combined chemosensing gains from organic amplifying materials and the lasing action, promise to deliver sensors that can detect explosives with unparalleled sensitivity.
Creation of patterned, efficient, and saturated color hybrid organic/inorganic quantum dot light emitting devices (QD-LEDs) is dependent on development of integrated fabrication and patterning methods for the QD layer. We show that micro-contact printing can be applied to QD deposition, generating micron-scale pattern definition, needed in pixilated-display applications. We demonstrate saturated color QD-LEDs with external quantum efficiencies in excess of 1%. Combining this technique with the use of wide optical band gap host materials, and a new synthetic route for the creation of blue emitting (CdS)ZnS nanocrystals, it is now possible to fabricate QD-LEDs with saturated color emission in the red, green and blue regions of the spectrum.
We review recent results form two types of small molecule organic light emitting devices (OLEDs). For flat panel display applications, we have developed a novel OLED pixel in which the R, G and B emission layers are vertically stacked to provide a simple fabrication process, minimum pixel size, and maximum fill factor. In separate experiments, we have worked towards achieving electrically- pumped organic lasers by demonstrating low-threshold lasing in an optically-pumped thin film double heterostructure consisting entirely of organic semiconducting materials.
We review recent progress in small molecule organic light emitting devices (OLEDs) with emphasis on their potential application to lightweight, head-up displays. We discuss OLEDs grown on thin, flexible, plastic substrates which may be bent over a radius of curvature of as little as 0.7 cm without damage and exhibit operating voltages and efficiencies similar to OLEDs grown on conventional glass substrates. Transparent OLEDs grown on such substrates create the potential for a new type of lightweight, full- color, OLED pixel in which the R, G and B emission layers are vertically stacked to provide a simple fabrication process, minimum pixel size, and maximum fill factor.
Image states on the surface of bare and adsorbate covered metals form simple, near-surface, bound electron systems. These systems provide useful model systems for understanding the electron- transfer dynamics between an adsorbate molecule and its underlying substrate. These states may be readily detected by two-photon photoemission, a technique ideally suited for high- resolution studies of excited surface states. Because of its relatively narrow linewidths, spectroscopy of the image states provides a useful method of detecting changes in surface and composition.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.