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256 results on '"Mativenga, Mallory"'

5. Composition‐Dependent High‐Performance Phototransistors Based on Solution Processed CH3NH3PbI3/ZnO Heterostructures.

Author

Haque, Farjana, Hasan, Md Mehedi, Bestelink, Eva, Sporea, Radu A., and Mativenga, Mallory

Subjects
PHOTOTRANSISTORS, HETEROSTRUCTURES, LEAD iodide, INDIUM gallium zinc oxide, ZINC oxide, VISIBLE spectra, PEROVSKITE, ZINC oxide films
Abstract

Recently, hybrid organic−inorganic perovskites have emerged as promising photo‐sensing materials for next‐generation solution‐processed phototransistors, achieving high responsivity, detectivity, and fast response. Here, a phototransistor that can detect visible light using a low‐cost, solution processed methylammonium lead iodide/zinc oxide (CH3NH3PbI3/ZnO) heterostructure is reported. While typical ZnO thin‐film transistors (TFTs) do not show any photocurrent under visible light illumination, CH3NH3PbI3 (MAPbI3) coated ZnO TFTs exhibit substantial photocurrent. Additionally, the optical, morphological, and structural characteristics of the light‐absorbing layers are further controlled by altering the precursor ratio of methylammonium iodide and lead (II) iodide (MAI:PbI2), which in turn affects the photosensitivity. Stoichiometric composition (MAI:PbI2 = 1:1) of MAPbI3 demonstrates optimal characteristics with a responsivity of 234 A/W and a high detectivity of 3.74 × 1013 Jones under white light illumination. The high photo‐responsivity and detectivity result from the combination of the suitable optoelectronic properties of the stoichiometric MAPbI3 film and its smooth interface with the ZnO channel. [ABSTRACT FROM AUTHOR]

Published
2023
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9. Compact X-Ray Tube With Ceramic Vacuum Seal for Portable and Robust Dental Imaging

Author

Gupta, Amar Prasad, primary, Choi, Jinho, additional, Mativenga, Mallory, additional, Park, Keunhwa, additional, Jang, Jaekyu, additional, Yeo, Seung Jun, additional, Jung, Jaeik, additional, Chae, Moon Shik, additional, Lee, Byeong-No, additional, Jang, Jejin, additional, Zhu, He-Lin, additional, Mok, Hyung-Soo, additional, Ahn, Jeung Sun, additional, and Ryu, Jehwang, additional

Published
2021
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12. A feasibility study of a portable intraoperative specimen imaging X‐ray system based on carbon nanotube field emitters

Author

Gupta, Amar Prasad, primary, Yeo, Seung Jun, additional, Mativenga, Mallory, additional, Jung, Jaeik, additional, Kim, Wooseob, additional, Lim, Jongmin, additional, Park, Junyoung, additional, Ahn, Jeung Sun, additional, Kim, Seung Hoon, additional, Chae, Moon Shik, additional, Yeon, Yeong Heum, additional, Kim, Namkug, additional, Ko, Beom‐Seok, additional, and Ryu, Jehwang, additional

Published
2021
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15. P‐25: Student Poster: Solution‐Processed CH3NH3PbI3/ZnO Phototransistor with High Photodetectivity.

Author

Haque, Farjana, Hasan, Md Mehedi, and Mativenga, Mallory

Subjects
PHOTOTRANSISTORS, ELECTRON transport, POSTERS, ZINC oxide, PEROVSKITE, ZINC oxide synthesis
Abstract

We report a phototransistor using the CH3NH3PbI3/ZnO heterostructure. The CH3NH3PbI3 (MAPbI3) and ZnO are deposited via low‐cost solution process. MAPbI3 coated ZnO TFTs exhibited enhanced photocurrent upon exposure to white light. The heterostructure formed between perovskite and ZnO, works as an efficient electron transport layer. The device had a responsivity of 195 A/W and a high detectivity of 1.10 × 1013 Jones under white light. The high photo‐responsivity and detectivity resulted from the combination of suitable optoelectronic property of MAPbI3 films and the high mobility of the spray coated ZnO films. [ABSTRACT FROM AUTHOR]

Published
2022
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27. Low Voltage Driven CMOS Circuits Based on Silicon on Glass

Author

Choi, Min Hyuk, primary, Choi, Jae Won, additional, Park, Seung Hyun, additional, Choi, Won Jae, additional, Mativenga, Mallory, additional, Jin, Jang, additional, Mruthyunjaya, Ravi, additional, J. Tredwell, Timothy, additional, Mozdy, Eric, additional, and Kosik Williams, Carlo, additional

Published
2019
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29. P‐25: Student Poster:Solution‐Processed CH3NH3PbI3/ZnO Phototransistor with High Photodetectivity

Author

Haque, Farjana, Hasan, Md Mehedi, and Mativenga, Mallory

Abstract

We report a phototransistor using the CH3NH3PbI3/ZnO heterostructure. The CH3NH3PbI3(MAPbI3) and ZnO are deposited via low‐cost solution process. MAPbI3coated ZnO TFTs exhibited enhanced photocurrent upon exposure to white light. The heterostructure formed between perovskite and ZnO, works as an efficient electron transport layer. The device had a responsivity of 195 A/W and a high detectivity of 1.10 × 1013Jones under white light. The high photo‐responsivity and detectivity resulted from the combination of suitable optoelectronic property of MAPbI3films and the high mobility of the spray coated ZnO films.

Published
2022
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30. Channel length dependence of negative-bias-illumination-stress in amorphous-indium-gallium-zinc-oxide thin-film transistors.

Author

Jae Gwang Um, Mativenga, Mallory, Migliorato, Piero, and Jin Jang

Subjects
*THIN film transistors, *ZINC oxide thin films, *SEMICONDUCTOR doping, *ELECTRON diffusion, *INDIUM oxide
Abstract

We have investigated the dependence of Negative-Bias-illumination-Stress (NBIS) upon channel length, in amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs). The negative shift of the transfer characteristic associated with NBIS decreases for increasing channel length and is practically suppressed in devices with L=100-μm. The effect is consistent with creation of donor defects, mainly in the channel regions adjacent to source and drain contacts. Excellent agreement with experiment has been obtained by an analytical treatment, approximating the distribution of donors in the active layer by a double exponential with characteristic length LD∼Ln∼10-μm, the latter being the electron diffusion length. The model also shows that a device with a non-uniform doping distribution along the active layer is in all equivalent, at low drain voltages, to a device with the same doping averaged over the active layer length. These results highlight a new aspect of the NBIS mechanism, that is, the dependence of the effect upon the relative magnitude of photogenerated holes and electrons, which is controlled by the device potential/band profile. They may also provide the basis for device design solutions to minimize NBIS [ABSTRACT FROM AUTHOR]

Published
2015
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34. Defect generation in amorphous-indium-gallium-zinc-oxide thin-film transistors by positive bias stress at elevated temperature.

Author

Jae Gwang Um, Mativenga, Mallory, Migliorato, Piero, and Jin Jang

Subjects
*THIN film transistors, *CATIONS, *HIGH temperatures, *INDIUM oxide, *ZINC oxide
Abstract

We report on the generation and characterization of a hump in the transfer characteristics of amorphous indium gallium zinc-oxide thin-film transistors by positive bias temperature stress. The hump depends strongly on the gate bias stress at 100 °C. Due to the hump, the positive shift of the transfer characteristic in deep depletion is always smaller that in accumulation. Since, the latter shift is twice the former, with very good correlation, we conclude that the effect is due to creation of a double acceptor, likely to be a cation vacancy. Our results indicate that these defects are located near the gate insulator/active layer interface, rather than in the bulk. Migration of donor defects from the interface towards the bulk may also occur under PBST at 100 °C. [ABSTRACT FROM AUTHOR]

Published
2014
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35. Design and Fabrication of CNT-Based E-Gun Using Stripe-Patterned Alloy Substrate for X-Ray Applications.

Author

Lim, Jongmin, Gupta, Amar P., Yeo, Seung Jun, Kong, Moonkyoo, Cho, Chong-Gil, Kim, Seung Hoon, Ahn, Jeung Sun, Mativenga, Mallory, and Ryu, Jehwang

Subjects
X-rays, FIELD emission, ALLOYS, ELECTRON gun, X-ray imaging
Abstract

We report the enhancement of carbon nanotube (CNT) field emitters by growing them directly on stripe-patterned alloy substrates. For a gate voltage of 1300 V, CNT field emitters grown on full and stripe-patterned alloy substrates achieved respective emission currents of 0.22 and 2.32 mA, corresponding to tenfold performance enhancement. Performance enhancement is attributed to the reduced screening effect (as a result of the spacing between strips) during field emission and a damage-free patterning process. To verify the ability of the stripe-patterned CNT field emitters to generate X-rays, we designed and assembled an electron gun through brazing. With the open type X-ray system, an X-ray image of human teeth was successfully obtained, verifying the potential of the stipe-patterned CNT emitters in X-ray applications. [ABSTRACT FROM AUTHOR]

Published
2019
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38. 56‐3: Student Paper:An Amplifier with Higher Gain Using Corbino—TFTs

Author

Lee, Woo-Rim, Jo, Jae-Hee, Mativenga, Mallory, Chung, Hoon-Ju, and Lee, Seung-Woo

Abstract

In this paper, an amplifier circuit using oxide TFTs for amplifying brain signal is proposed. The proposed circuit is largely composed of two TFTs. It consists of a driving transistor that receives an input and a load transistor that determines the voltage gain through interaction with the driving transistor. Based on depletion load inverting amplifier, we analyzed the small signal modeled circuit. By using a circular TFT called Corbino‐TFT, we were able to obtain a greater voltage gain. The measurement results were compared with the calculated voltage gain. In addition, to get a higher gain, method of connecting two amplifiers in series is presented and simulation results are also presented.

Published
2021
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