High-performance Image Sensors Research Articles

AWafer-Scale Nanoporous 2D Active Pixel Image Sensor Matrix with High Uniformity, High Sensitivity, and Rapid Switching.

2D transition-metal dichalcogenides (TMDs) havebeen successfully developed as novel ubiquitous optoelectronics owing to their excellent electrical and optical characteristics. However, active-matrix image sensors based on TMDs have limitations owing to the difficulty of fabricating large-area integrated circuitry and achieving high optical sensitivity. Herein, a large-area uniform, highly sensitive, and robust image sensor matrix with active pixels consisting of nanoporous molybdenum disulfide (MoS2 ) phototransistors and indium-gallium-zinc oxide (IGZO) switching transistors is reported. Large-area uniform 4-inch wafer-scale bilayer MoS2 films are synthesized by radio-frequency (RF) magnetron sputtering and sulfurization processes and patterned to be a nanoporous structure consisting of an array of periodic nanopores on the MoS2 surface via block copolymer lithography. Edge exposure on the nanoporous bilayer MoS2 induces the formation of subgap states, which promotes a photogating effect to obtain an exceptionally high photoresponsivity of 5.2 × 104 A W-1 . A 4-inch-wafer-scale image mapping is successively achieved using this active-matrix image sensor by controlling the device sensing and switching states. The high-performance active-matrix image sensor is state-of-the-art in 2D material-based integrated circuitry and pixel image sensor applications.

Correction to Probing the Efficacy of Large-Scale Nonporous IGZO for Visible-to-NIR Detection Capability: An Approach toward High-Performance Image Sensor Circuitry

Correction to Probing the Efficacy of Large-Scale Nonporous IGZO for Visible-to-NIR Detection Capability: An Approach toward High-Performance Image Sensor Circuitry

Highly aligned organic microwire crystal arrays for high-performance polarization-sensitive photodetectors and image sensors

Organic semiconductors with excellent optoelectronic properties are important building blocks for high-performance organic devices. Patterning organic crystals with high precision and accurately positioning them at the target position are major challenges for integrated devices. However, uncontrollable dewetting of the conventional solution method leads to as-prepared micro-nanocrystals with high defect-state density, low crystalline quality, and disordered distribution, which impair the uniformity of the device performance and limit integration. By regulating the solution position with a template and guiding the solution flow direction under gravity, aligned organic microwire arrays and polygonal patterns were fabricated. The polarization-sensitive photodetector exhibited responsivity up to 1234 A W−1, linear dynamic range of 148 dB, Iphoto/Idark of 104, response time as low as 1.1 ms, and dichroic ratio up to 2.1. Given the homogeneity of microwire arrays, the device-to-device variation was reduced to 3.58%, resulting in high-quality imaging. This study provides new insights into organic micro/nanocrystal patterning and device integration.

Probing the Efficacy of Large-Scale Nonporous IGZO for Visible-to-NIR Detection Capability: An Approach toward High-Performance Image Sensor Circuitry.

The technological ability to detect a wide spectrum range of illuminated visible-to-NIR is substantially improved for an amorphous metal oxide semiconductor, indium gallium zinc oxide (IGZO), without employing an additional photoabsorber. The fundamentally tuned morphology via structural engineering results in the creation of nanopores throughout the entire thickness of ∼30 nm. See-through nanopores have edge functionalization with vacancies, which leads to a large density of substates near the conduction band minima and valence band maxima. The presence of nanoring edges with a high concentration of vacancies is investigated using chemical composition analysis. The process of creating a nonporous morphology is sophisticated and is demonstrated using a wafer-scale phototransistor array. The performance of the phototransistors is assessed in terms of photosensitivity (S) and photoresponsivity (R); both are of high magnitudes (S = 8.6 × 104 at λex = 638 nm and Pinc = 512 mW cm2-; R = 120 A W1- at Pinc = 2 mW cm2- for the same λex). Additionally, the 7 × 5 array of 35 phototransistors is effective in sensing and reproducing the input image by responding to selectively illuminated pixels.

Patterning of Wafer-Scale MXene Films for High-Performance Image Sensor Arrays.

As a rapidly growing family of 2D transition metal carbides and nitrides, MXenes are recognized as promising materials for the development of future electronics and optoelectronics. So far, the reported patterning methods for MXene films lack efficiency, resolution, and compatibility, resulting in limited device integration and performance. Here, a high-performance MXene image sensor array fabricated by a wafer-scale combination patterning method of an MXene film is reported. This method combines MXene centrifugation, spin-coating, photolithography, and dry-etching and is highly compatible with mainstream semiconductor processing, with a resolution up to 2µm, which is at least 100 times higher than other large-area patterning methods reported previously. As a result, a high-density integrated array of 1024-pixel Ti3 C2 Tx /Si photodetectors with a detectivity of 7.73 × 1014 Jones and a light-dark current ratio (Ilight /Idark ) of 6.22 × 106 , which is the ultrahigh value among all reported MXene-based photodetectors, is fabricated. This patterning technique paves a way for large-scale high-performance MXetronics compatible with mainstream semiconductor processes.

Тенденції розвитку сенсорних приладів на основі поверхневого плазмонного резонансу

Trends in the development of modern sensory devices based on surface plasmon resonance (SPR) are considered. The basic principles of construction of SPR sensor are given. For excitation of surface plasmons on the surface of sensitive elements of biosensory, a prism of total internal reflection is used or a dielectric substrate are used. A thin (dozens nm) film of high-conductive metal (mainly gold or silver) is applied to the working surface of the prisms or dielectric substrate. In a typical observation experiment, SPR is measured dependence on the angle of increasing light intensity, reflected by the resonance sensitive surface of the prism (chip). The optical schemes and principles of work of various SPR sensors are considered: - SPR Sensors with angular modulation, which are the most commonly used method based on the corner registration, in which the SPR occurs. The surface of the metal film is irradiated by monochromatic light and scans on a certain range of angles. There is a kind of SPR sensors with angular modulation, in which there is no mechanical scan of the angle of fall. Such sensors are entirely necessary for excitation of PPRs a set of angles is obtained due to a divergent or convergent light beam. - PPR sensors with a wavelength modulation is based on fixing an angle of falling light at a certain value and modulation of the wavelength of the incident light. Excitation of surface plasmons leads to a characteristic failure in the spectrum of reflected radiation. - Phase sensitive SPR sensors in which a change in the phase of the light wave associated with the surface plasma is measured on one corner of the fall and the wavelength of the light wave and is used as the output signal. - SPR imaging sensors in which the Technology of SPR imaging (SPRi) combines the sensitivity of the SPR with spatial image capabilities. The SPRI circuit uses as a fixed angle (as a rule, a slightly left angle of the SPR) and a fixed wavelength to measure changes in the reflection ability (Δ% R) that occur when the curve of the SPR is shifted due to the change in the refractive index above the surface of the sensor element. - SPR imaging sensors polarization contrast. In order to improve the quality of high-performance SPR imaging sensors in terms of sensitivity and resolution, the method of polarization contrast is used Disadvantages and advantages of SPR sensors are constructed with different principles are considered. The design and prospect of the use of achromatic and suburchast wave plates in the PPR imaging sensors with polarization contrast are considered.

Synthesis and Physical Properties of New Blue Color Filter Dye Using on Triarylmethine Moiety for Image Sensors.

In this study, a triarylmethine derivative of DMCEBA-BTSA with the high thermal and chemical stability was newly synthesized in order to develop a high-performance image sensor. It showed a high transmittance of more than 80% at 450 nm and △Eab showed a very low color difference of 2.32 after thermal treatment. In solvent resistance, transmittance of 90% was not changed and △Eab showed a low color difference of 0.67 before and after solvent dipping. As a results of the migration test, there was no change at all after dipping in the PGMEA transmittance spectrum. It was confirmed that the newly synthesized blue colorant exhibited excellent thermal and chemical stability and it could be applied to image sensor color filter application as the blue color.

Synthesis and Physical Properties of New Violet Color Filter Dye for Image Sensors.

New violet colorant, XPDIA was synthesized by using Acid Red 52 to develop a high-performance image sensor. Solubility of XPDIA was more than 5 wt% in PGMEA which is the main solvent in the color filter preparation process. △Eab value of XPDIA showed a very low color difference of 2.17 after thermal treatment. In solvent resistance, transmittance was not changed and △Eab showed a low color difference of 1.55 before and after solvent dipping. As a result of the migration test, there was no change at all after dipping in the PGMEA transmittance spectrum. The newly synthesized violet colorant, XPDIA exhibited excellent thermal-chemical stability, and good solubility and it can be applied to image sensor color filter application.

New blended blue colorants based on triarylmethine dye and anthraquinone pigment for image sensors

As the electronic device market has expanded, image sensors have attracted much attention. In order to develop a high performance image sensor, the unit pixel size of the image sensor is gradually decreasing. In order to make the decreased pixel size, the method using the pigment mill base has a limitation in finely dividing the particles, and a method using a dye which is soluble in a solvent is required. In this study, blue photoresist mixture (1:1 wt%) using a dye and a pigment was prepared by mixing a blue dye of ABD having high optical property and a blue pigment of PAQ having high thermal and chemical stability. After commercial thermal treatment of photoresist mixture, transmittance showed more than 80% and △Eab of ABD-PAQ was 1.50, which is superior thermal property to ABD. In case of chemical stability treatment, △Eab values of ABD and ABD-PAQ were 0.86 and 0.66, which means that ABD-PAQ shows high chemical stability. These improvement comes from the high thermal and chemical stability of PAQ moiety as well as the high absorption property of ABD moiety. As a result, it was confirmed that the blue hybrid spin-coated film mixed with the blue dye and the pigment showed excellent thermal stability compared with the dye-based spin-coated flim.

Synthesis and Blue Pixel Property of New Violet Dye for Image Sensors.

In this study, a blue photoresist with the hybrid dye-pigment system was developed by mixing xanthene-based dye (XPDIA) and blue pigment 15:6 (1:1, 5 wt% of total mixture amount) in order to develop high-performance image sensors with high thermal and chemical stability. The colorant used in this study has the nano-sized particle of around 100 nm and the physical property is related with the photonic property in image sensor application such as the cameras of mobile phone, car black box, security, etc. The hybrid dye-pigment system showed a high transmittance of more than 90% at 450 nm, and Δab showed very low color difference of 0.52. In solvent resistance, high transmittance of 90% was perfectly maintained, and Δab showed low color difference of 1.08. Migration test result exhibited no change at all after dipping in PGMEA transmittance spectrum. These results are due to the high absorption optical properties of XPDIA dye in the HDPS and the high thermal and chemical stability properties of the PB15:6 pigment. As a result, it was confirmed that the mixed blue hybrid spin coating film exhibited excellent thermal and chemical stability as well as good optical property.

Compressive Sampling for Array Cameras

While design of high-performance lenses and image sensors has long been the focus of camera development, the size, weight, and power of image data processing components are currently the primary barriers to radical improvements in camera resolution. Here we show that deep learning--aided compressive sampling can reduce operating power on camera head electronics by 20 times or more. Traditional compressive sampling has to date been primarily applied in the physical sensor layer. We show here that with the aid of deep learning algorithms, compressive sampling is offers unique power management advantages in digital layer compression.

Direct Tellurization of Pt to Synthesize 2D PtTe2 for High-Performance Broadband Photodetectors and NIR Image Sensors.

Platinum telluride (PtTe2) has garnered significant research enthusiasm owing to its unique characteristics. However, large-scale synthesis of PtTe2 toward potential photoelectric and photovoltaic application has not been explored yet. Herein, we report direct tellurization of Pt nanofilms to synthesize large-area PtTe2 films and the influence of growth conditions on the morphology of PtTe2. Electrical analysis reveals that the as-grown PtTe2 films exhibit typical semimetallic behavior, which is in agreement with the results of first-principles density functional theory (DFT) simulation. Moreover, the combination of multilayered PtTe2 and Si results in the formation of a PtTe2/Si heterojunction, exhibiting an obvious rectifying effect. Moreover, the PtTe2-based photodetector displays a broadband photoresponse to incident radiation in the range of 200-1650 nm, with the maximum photoresponse at a wavelength of ∼980 nm. The R and D* of the PtTe2-based photodetector are found to be 0.406 A W-1 and 3.62 × 1012 Jones, respectively. In addition, the external quantum efficiency is as high as 32.1%. On the other hand, the response time of τrise and τfall is estimated to be 7.51 and 36.7 μs, respectively. Finally, an image sensor composed of a 8 × 8 PtTe2-based photodetector array was fabricated, which can record five near-infrared (NIR) images under 980 nm with a satisfying resolution. The result demonstrates that the as-prepared PtTe2 material will be useful for application in NIR optoelectronics.

Fabrication of Multi-stacked Integrated Circuit for High-Performance Image Sensors

Fabrication of Multi-stacked Integrated Circuit for High-Performance Image Sensors

CVD growth of perovskite/graphene films for high-performance flexible image sensor

Hybrid perovskite possesses excellent photoelectric properties, including large light-absorption capacity and high carrier mobility, and is an ideal light-absorbing material for photoelectric devices. The grain size and compactness of hybrid perovskite are key factors affecting the performance of photoelectric devices. The photocurrent and photoresponsivity of these devices are relatively low because of the rapidly recombined photoexcited electron-hole pairs in hybrid perovskite. Herein, we develop a facile two-step chemical vapor deposition (CVD) method to synthesize a high-quality van der Waals (vdWs) MAPbI3/graphene heterostructure for high-performance image sensor. We introduced inorganic sources (PbI2) to vdWs epitaxially grown PbI2 film on a seamless graphene monolayer film template through CVD. Methylammonium iodide (MAI) was then reintroduced to prepare the vdWs MAPbI3/graphene heterostructure. The MAPbI3 layer is composed of densely packed, large-size grains and displays a smooth surface. High photoresponsivity of 107 A/W is achieved in the corresponding photodetector. Inspired by the human visual system, we designed a flexible photodetector array containing (24 × 24) pixels, achieving perfect image recognition and color discrimination. Our study may greatly facilitate the construction of high-performance optoelectronic devices in artificial retina, biomedical imaging, remote sensing, and optical communication.

Toward Broadband Imaging: Surface-Engineered PbS Quantum Dot/Perovskite Composite Integrated Ultrasensitive Photodetectors.

PbS colloidal quantum dots passivated by the thiocyanate anion (SCN-) are developed to combine with perovskite (CH3NH3PbI3) as building blocks for UV-vis-NIR broadband photodetectors. Both high electrical conductivity and appropriate energy-level alignment are obtained by the in situ ligand exchange with SCN-. The PbS-SCN/CH3NH3PbI3 composite photodetectors are sensitive to a broad wavelength range covering the UV-vis-NIR region (365-1550 nm), possessing an excellent responsivity of 255 A W-1 at 365 nm and 1.58 A W-1 at 940 nm, remarkably high detectivity of 4.9 × 1013 Jones at 365 nm and 3.0 × 1011 Jones at 940 nm, and fast response time of ≤42 ms. Furthermore, a 10 × 10 photodetector array is fabricated and integrated, which constitutes a high-performance broadband image sensor. Our approach paves a way for the development of highly sensitive broadband photodetectors/imagers that can be easily integrated.

High-Detectivity Perovskite Light Detectors Printed in Air from Benign Solvents

Summary Here, we propose a simple and low-temperature approach for the synthesis of methylammonium lead halide perovskite inks based on sub-micrometer-sized particles with tunable band gap. The particles allow the formulation of inks in benign solvents, such as propan-2-ol, and the printing of the photoactive layers of planar photoconductors with scalable, large-area coating techniques under ambient conditions. When surface traps are passivated with [6,6]-phenyl-C61-butyric acid methyl ester fullerene (PCBM), a high photoconductive gain (exceeding 200 in the blue) and reduced noise produce record-high specific detectivities exceeding 7 × 1013 cmHz0.5/W and gain-bandwidth product values of 7.5 × 106 Hz. Given the extreme simplicity of the presented device architecture and the straightforward processing, yielding printable light detectors rivalling established technologies, the present work promises a short-term deployment of printed perovskite detectors in a multitude of opto-electronic applications.

High performance active image sensor pixel design with circular structure oxide TFT

We report a high-performance active image sensor pixel design by utilizing amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) with a circular structure. The TFT, configured with the inner electrode as source and outer electrode as drain, typically exhibits good saturation electrical characteristics, where the device has a constant drive current despite variations in drain voltage. Due to the very high output resistance exhibited by this asymmetric TFT structure with a circular shape, the pixel circuit considered here in common-drain configuration provides a higher gain of operation than a pixel circuit implemented with rectangular a-IGZO TFTs. They can be used as driving TFTs in active image sensor circuits. They are, therefore, good candidates for digital X-ray detectors in applications such as medical diagnostic procedures.

Distributed Parallel Super-Block-Based Star Detection and Centroid Calculation

Due to the inadequacies of the speed of star detection and centroid calculation (SDCC), the applications of high-resolution and high-frame-rate image sensors are greatly limited in star trackers, restricting the performance of the star trackers. To resolve this problem, a novel distributed parallel super-block-based SDCC method is proposed in this paper. In contrast to the previous SDCC methods, the proposed method divides the star images into several sub-images and processes these sub-images in parallel. Then, by using a super-block-based method and a distributed shared memory-based method to process the stars in sub-images (sub-stars) and in adjacent sub-images (boundary stars), respectively, the position information of all the stars are detected during the parallel scan of the sub-images. The proposed method exhibits a speed that is up to $4 \,\, \times $ M times faster than the previous SDCC methods in processing the star images that are divided into M sub-images. Experimental results demonstrate that the proposed method is correct and effective. It is applicable to the use of most high-performance image sensors and resolves the performance limitation of star trackers to achieve better attitude accuracy and attitude update rate.

High responsivity middle-wavelength infrared graphene photodetectors using photo-gating

In this work, high-responsivity graphene photodetectors operating in the middle-wavelength infrared (MWIR) spectral band were fabricated by taking advantage of the photo-gating effect. Graphene-based field effect transistors were fabricated on indium antimonide (InSb) substrates. The InSb generated photo-carriers in response to incident IR light modulated the graphene channel gate voltage and induced a large photocurrent. These graphene-based photodetectors exhibited a clear photoresponse during irradiation with 4.6 μm MWIR laser light and an ultrahigh responsivity of 33.8 A/W was achieved at 50 K due to the photo-gating effect. These devices were found to maintain an MWIR photoresponse up to 150 K. Our graphene-based photodetector design is expected to contribute to the development of high-performance MWIR image sensors.

Separating light absorption layer from channel in ZnO vertical nanorod arrays based photodetectors for high-performance image sensors

Photoconductor arrays with both high responsivity and large ON/OFF ratios are of great importance for the application of image sensors. Herein, a ZnO vertical nanorod array based photoconductor with a light absorption layer separated from the device channel has been designed, in which the photo-generated carriers along the axial ZnO nanorods drive to the external electrodes through nanorod-nanorod junctions in the dense layer at the bottom. This design allows us to enhance the photocurrent with unchanged dark current by increasing the ratio between the ZnO nanorod length and the thickness of the dense layer to achieve both high responsivity and large ON/OFF ratios. As a result, the as-fabricated devices possess a high responsivity of 1.3 × 105 A/W, a high ON/OFF ratio of 790, a high detectivity of 1.3 × 1013 Jones, and a low detectable light intensity of 1 μW/cm2. More importantly, the developed approach enables the integration of ZnO vertical nanorod array based photodetectors as image sensors with uniform device-to-device performance.