Memory and Coupling in Nanocrystal Optoelectronic Devices

Optoelectronic devices incorporating semiconducting nanocrystals are promising for many potential applications. Nanocrystals whose size is below the exciton Bohr radius have optical absorption and emission that is tunable with size, due to the quantum confinement of the charge carriers. However, the same confinement that yields these optical properties also makes electrical conduction in a film of nanocrystals occur via tunneling, due to the high energy barrier between nanocrystals. Hence, the extraction of photo-generated charge carriers presents a significant challenge. Several approaches to optimizing the reliability and efficiency of optoelectronic devices using semiconducting nanocrystals are explored herein. Force microscopy is used to investigate charge behavior in nanocrystal films. Plasmonic structures are lithographically defined to enhance electric field and thus charge collection efficiency in two-electrode nanocrystal devices illuminated at plasmonically resonant wavelengths. Graphene substrates are shown to couple electronically with nanocrystal films, improving device conduction while maintaining carrier quantum confinement within the nanocrystal. And finally, the occupancy of charge carrier traps is shown to both directly impact the temperature-dependent photocurrent behavior, and be tunable using a combination of illumination and electric field treatments. Trap population manipulation is robustly demonstrated and verified using a variety of wavelength, intensity, and time-dependent measurements of photocurrent in nanogap nanocrystal devices, emphasizing the importance of measurement history and the possibility of advanced device behavior tuning based on desired operating conditions. Each of these experiments reveals a path toward understanding and optimizing semiconducting nanocrystal optoelectronic devices

Characterization of Memory and Measurement History in Photoconductivity of Nanocyrstal Arrays

Photoconductivity in nanocrystal films has been previously characterized, but memory effects have received little attention despite their importance for device applications. We show that the magnitude and temperature dependence of the photocurrent in CdSe/ZnS core-shell nanocrystal arrays depends on the illumination and electric field history. Changes in photoconductivity occur on a few-hour timescale, and subband gap illumination of nanocrystals prior to measurements modifies the photocurrent more than band gap illumination. The observed effects can be explained by charge traps within the band gap that are filled or emptied, which may alter nonradiative recombination processes and affect photocurrent

Orientation selectivity in a multi-gated organic electrochemical transistor.

UNLABELLED: Neuromorphic devices offer promising computational paradigms that transcend the limitations of conventional technologies. A prominent example, inspired by the workings of the brain, is spatiotemporal information processing. Here we demonstrate orientation selectivity, a spatiotemporal processing function of the visual cortex, using a poly(3,4ethylenedioxythiophene):poly(styrene sulfonate) ( PEDOT: PSS) organic electrochemical transistor with multiple gates. Spatially distributed inputs on a gate electrode array are found to correlate with the output of the transistor, leading to the ability to discriminate between different stimuli orientations. The demonstration of spatiotemporal processing in an organic electronic device paves the way for neuromorphic devices with new form factors and a facile interface with biology

Improved Spatial Resolution in Thick, Fully-Depleted CCDs withEnhanced Red Sensitivity

The point spread function (PSF) is an important measure of spatial resolution in CCDs for point-like objects, since it affects image quality and spectroscopic resolution. We present new data and theoretical developments for lateral charge diffusion in thick, fully-depleted charge-coupled devices (CCDs) developed at Lawrence Berkeley National Laboratory (LBNL). Because they can be over-depleted, the LBNL devices have no field-free region and diffusion is controlled through the application of an external bias voltage. We give results for a 3512 x 3512 format, 10.5 {micro}m pixel back-illuminated p-channel CCD developed for the SuperNova/Acceleration Probe (SNAP), a proposed satellite-based experiment designed to study dark energy. The PSF was measured at substrate bias voltages between 3 V and 115 V. At a bias voltage of 115 V, we measure an rms diffusion of 3.7 {+-} 0.2 {micro}m. Lateral charge diffusion in LBNL CCDs will meet the SNAP requirements

Game-based learning to engage students with physics and astronomy using a board game

In this research article, the authors developed a novel astronomy board game and examined how this approach could facilitate the learning and teaching of astronomy topics covered in the new Irish Science Syllabus. A total of 119 post-primary students took part in the pilot trial across Ireland. Data was collected via feedback questionnaires, systematic observations and pre and post-test surveys. Results indicate that this astronomy board game significantly enhances students knowledge of astronomy concepts and perceptions of scientists. Furthermore, teachers showed positive attitudes towards this approach for teaching astronomy. Additionally, the game was demonstrated as a useful learning tool and as an activity to promote social skills. The findings offer a promising basis for further exploration of the integration of game-based approaches to physics education to promote active participation and interaction, balancing the learning objectives with play.This work was supported by CAPES-Brazil scholarship number {88881.128466/2016-01}. We would like to thank the Institute of Physics in Ireland for their support. A special thanks to all students and teachers who participated in this research.peer-reviewe

Nanoelectronics

Nanomaterials are changing the world we live in, and one of the most exciting applications they can have is the creation of new electronic devices. But what are they, how can we build devices from them, and how can nanoelectronics give us new ways to interact with light, our environments and even our brains? This ebook will explore the unique physics of different types of nanomaterials, and lay out different devices that harness this unique physics to create optoelectronic components, chemical sensors, and novel paradigms for memory and computing. After outlining the current state of the art, the final section looks to grand challenges and opportunities in nanoelectronics

Improved Spatial Resolution in Thick, Fully-Depleted CCDs with Enhanced Red Sensitivity

The point spread function (PSF) is an important measure of spatial resolution in CCDs for point-like objects, since it can affect use in imaging and spectroscopic applications. We present new data and theoretical developments in the study of lateral charge diffusion in thick, fully-depleted charge-coupled devices (CCDs) developed at Lawrence Berkeley National Laboratory (LBNL). Because they are fully depleted, the LBNL devices have no field-free region, and diffusion can be controlled through the application of an external bias voltage. We give results for a 3512x3512 format, 10.5 ?m pixel back-illuminated p-channel CCD developed for the SuperNova/ Acceleration Probe (SNAP), a proposed satellite-based experiment designed to study dark energy. The PSF was measured at substrate bias voltages between 3 V and 115 V. At a bias voltage of 115V, we measure an rms diffusion of 3.7 +- 0.2 ?m. Lateral charge diffusion in LBNL CCDs is thus expected to meet the SNAP requirements