fabrication-ultra-thin-color-films-with-highly-absorbing-media-using

Fabrication of Ultra-thin Color Films with Highly Absorbing Media Using Oblique Angle Deposition

Ultra-thin film structures have been studied extensively for use as optical coatings, but performance and fabrication challenges remain.&#160; We present ...

fabrication-flexible-image-sensor-based-on-lateral-nipin

Fabrication of Flexible Image Sensor Based on Lateral NIPIN Phototransistors

Flexible photodetectors have been intensely studied for the use of curved image sensors, which are a crucial component in bio-inspired imaging systems, ...

Gwangju Institute of Science and Technology

We demonstrate ultra-thin, fine-tunable optical coatings with enhanced color purity based on highly absorbent porous media on a metal substrate. We show that the color range provided by these ultra-thin film coatings can be extended by making the absorptive dielectric layer porous. Oblique angle deposition (OAD) of a thin (10-25 nm) germanium (Ge) film by e-beam evaporation onto a thick gold substrate yields controlled porosity. Reflectance spectra and color representations from both calculations and experiments verify the enhancement of resonance tunability and color purity in the nano-tailored coatings. Angle independent reflection properties, and the applicability of such porous Ge on various metal substrates, indicate the strength of these concepts.

Ultra-thin films with highly absorbent porous media fine-tunable for coloration and enhanced color purity.

Curved image sensors, which are a key component in bio-inspired imaging systems, have been widely studied because they can improve an imaging system in various aspects such as low optical aberrations, small-form, and simple optics configuration. Many methods and materials to realize a curvilinear imager have been proposed to address the drawbacks of conventional imaging/optical systems. However, there have been few theoretical studies in terms of electronics on the use of a lateral photodetector as a flexible image sensor. In this paper, we demonstrate the applicability of a Si-based lateral phototransistor as the pixel of a high-efficiency curved photodetector by conducting various electrical simulations with technology computer aided design (TCAD). The single phototransistor is analyzed with different device parameters: the thickness of the active cell, doping concentration, and structure geometry. This work presents a method to improve the external quantum efficiency (EQE), linear dynamic range (LDR), and mechanical stability of the phototransistor. We also evaluated the dark current in a matrix form of phototransistors to estimate the feasibility of the device as a flexible image sensor. Moreover, we fabricated and demonstrated an array of phototransistors based on our study. The theoretical study and design guidelines of a lateral phototransistor create new opportunities in flexible image sensors.

Parametric Optimization of Lateral NIPIN Phototransistors for Flexible Image Sensors.

Soft bioelectronic devices provide new opportunities for next-generation implantable devices owing to their soft mechanical nature that leads to minimal tissue damages and immune responses. However, a soft form of the implantable optoelectronic device for optical sensing and retinal stimulation has not been developed yet because of the bulkiness and rigidity of conventional imaging modules and their composing materials. Here, we describe a high-density and hemispherically curved image sensor array that leverages the atomically thin MoS-graphene heterostructure and strain-releasing device designs. The hemispherically curved image sensor array exhibits infrared blindness and successfully acquires pixelated optical signals. We corroborate the validity of the proposed soft materials and ultrathin device designs through theoretical modeling and finite element analysis. Then, we propose the ultrathin hemispherically curved image sensor array as a promising imaging element in the soft retinal implant. The CurvIS array is applied as a human eye-inspired soft implantable optoelectronic device that can detect optical signals and apply programmed electrical stimulation to optic nerves with minimum mechanical side effects to the retina.

ArticleTotal : 2	Year
Publication title Cited by 2	2017
Publication title	2018

Article	Year
Ultra-thin films with highly absorbent porous media fine-tunable for coloration and enhanced color purity. Nanoscale\| PubMed ID: 28045180	2017
Parametric Optimization of Lateral NIPIN Phototransistors for Flexible Image Sensors. Sensors (Basel, Switzerland)\| PubMed ID: 28767076	2017
Human eye-inspired soft optoelectronic device using high-density MoS-graphene curved image sensor array. Nature communications\| PubMed ID: 29162854	2017

Gil Ju Lee

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