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Start Over "DOT" Publication Type Academic Journals Journal nature communications
19,398 results on '"DOT"'

13. Incoherent nonadiabatic to coherent adiabatic transition of electron transfer in colloidal quantum dot molecules

Author

Hou, Bokang, Thoss, Michael, Banin, Uri, and Rabani, Eran

Subjects
Quantum Physics, Chemical Sciences, Physical Chemistry, Theoretical and Computational Chemistry, Physical Sciences, Atomic, Molecular and Optical Physics, MSD-General, MSD-C2SEPEM
Abstract

Electron transfer is a fundamental process in chemistry, biology, and physics. One of the most intriguing questions concerns the realization of the transitions between nonadiabatic and adiabatic regimes of electron transfer. Using colloidal quantum dot molecules, we computationally demonstrate how the hybridization energy (electronic coupling) can be tuned by changing the neck dimensions and/or the quantum dot sizes. This provides a handle to tune the electron transfer from the incoherent nonadiabatic regime to the coherent adiabatic regime in a single system. We develop an atomistic model to account for several states and couplings to the lattice vibrations and utilize the mean-field mixed quantum-classical method to describe the charge transfer dynamics. Here, we show that charge transfer rates increase by several orders of magnitude as the system is driven to the coherent, adiabatic limit, even at elevated temperatures, and delineate the inter-dot and torsional acoustic modes that couple most strongly to the charge transfer dynamics.

Published
2023

24. Emergence of distinct electronic states in epitaxially-fused PbSe quantum dot superlattices

Author

Kavrik, Mahmut S, Hachtel, Jordan A, Ko, Wonhee, Qian, Caroline, Abelson, Alex, Unlu, Eyup B, Kashyap, Harshil, Li, An-Ping, Idrobo, Juan C, and Law, Matt

Subjects
Engineering, Physical Sciences, Materials Engineering, Nanotechnology, Condensed Matter Physics
Abstract

Quantum coupling in arrayed nanostructures can produce novel mesoscale properties such as electronic minibands to improve the performance of optoelectronic devices, including ultra-efficient solar cells and infrared photodetectors. Colloidal PbSe quantum dots (QDs) that self-assemble into epitaxially-fused superlattices (epi-SLs) are predicted to exhibit such collective phenomena. Here, we show the emergence of distinct local electronic states induced by crystalline necks that connect individual PbSe QDs and modulate the bandgap energy across the epi-SL. Multi-probe scanning tunneling spectroscopy shows bandgap modulation from 0.7 eV in the QDs to 1.1 eV at their necks. Complementary monochromated electron energy-loss spectroscopy demonstrates bandgap modulation in spectral mapping, confirming the presence of these distinct energy states from necking. The results show the modification of the electronic structure of a precision-made nanoscale superlattice, which may be leveraged in new optoelectronic applications.

Published
2022

31. Emergence of distinct electronic states in epitaxially-fused PbSe quantum dot superlattices

Author

Mahmut S. Kavrik, Jordan A. Hachtel, Wonhee Ko, Caroline Qian, Alex Abelson, Eyup B. Unlu, Harshil Kashyap, An-Ping Li, Juan C. Idrobo, and Matt Law

Subjects
Science
Abstract

Self-assembled PbSe quantum dot (QD) superlattices are a class of materials that promises novel mesoscale electronic properties due to electronic coupling between individual QDs. Here, the authors reveal distinct electronic states manifested by the quantum confinement of charge carriers in epitaxially formed necking between QDs.

Published
2022
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32. Versatile stochastic dot product circuits based on nonvolatile memories for high performance neurocomputing and neurooptimization.

Author

Mahmoodi, MR, Prezioso, M, and Strukov, DB

Abstract

The key operation in stochastic neural networks, which have become the state-of-the-art approach for solving problems in machine learning, information theory, and statistics, is a stochastic dot-product. While there have been many demonstrations of dot-product circuits and, separately, of stochastic neurons, the efficient hardware implementation combining both functionalities is still missing. Here we report compact, fast, energy-efficient, and scalable stochastic dot-product circuits based on either passively integrated metal-oxide memristors or embedded floating-gate memories. The circuit's high performance is due to mixed-signal implementation, while the efficient stochastic operation is achieved by utilizing circuit's noise, intrinsic and/or extrinsic to the memory cell array. The dynamic scaling of weights, enabled by analog memory devices, allows for efficient realization of different annealing approaches to improve functionality. The proposed approach is experimentally verified for two representative applications, namely by implementing neural network for solving a four-node graph-partitioning problem, and a Boltzmann machine with 10-input and 8-hidden neurons.

Published
2019

37. Optically pumped colloidal-quantum-dot lasing in LED-like devices with an integrated optical cavity.

Author

Roh, Jeongkyun, Park, Young-Shin, Lim, Jaehoon, and Klimov, Victor I

Abstract

Realization of electrically pumped lasing with solution processable materials will have a revolutionary impact on many disciplines including photonics, chemical sensing, and medical diagnostics. Due to readily tunable, size-controlled emission wavelengths, colloidal semiconductor quantum dots (QDs) are attractive materials for attaining this goal. Here we use specially engineered QDs to demonstrate devices that operate as both a light emitting diode (LED) and an optically pumped laser. These structures feature a distributed feedback resonator integrated into a bottom LED electrode. By carefully engineering a refractive-index profile across the device, we are able to obtain good confinement of a waveguided mode within the QD medium, which allows for demonstrating low-threshold lasing even with an ultrathin (about three QD monolayers) active layer. These devices also exhibit strong electroluminescence (EL) under electrical pumping. The conducted studies suggest that the demonstrated dual-function (lasing/EL) structures represent a promising device platform for realizing colloidal QD laser diodes.

Published
2020

40. Wafer-scale epitaxial modulation of quantum dot density

Author

Bart, N., Dangel, C., Zajac, P., Spitzer, N., Ritzmann, J., Schmidt, M., Babin, H. G., Schott, R., Valentin, S. R., Scholz, S., Wang, Y., Uppu, R., Najer, D., Löbl, M. C., Tomm, N., Javadi, A., Antoniadis, N. O., Midolo, L., Müller, K., Warburton, R. J., Lodahl, P., Wieck, A. D., Finley, J. J., and Ludwig, A.

Published
2022
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41. Atomically dispersed Pb ionic sites in PbCdSe quantum dot gels enhance room-temperature NO2 sensing

Author

Xin Geng, Shuwei Li, Lalani Mawella-Vithanage, Tao Ma, Mohamed Kilani, Bingwen Wang, Lu Ma, Chathuranga C. Hewa-Rahinduwage, Alina Shafikova, Eranda Nikolla, Guangzhao Mao, Stephanie L. Brock, Liang Zhang, and Long Luo

Subjects
Science
Abstract

Quantum dot-based NO2 sensors often suffer from low sensitivity or long recovery times. Here, the authors report that bimetallic PbCdSe quantum dot gels containing atomically dispersed Pb ionic sites enable ultra-sensitive and fast NO2 sensing.

Published
2021
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43. Surface state-induced barrierless carrier injection in quantum dot electroluminescent devices

Author

Hyeonjun Lee, Byeong Guk Jeong, Wan Ki Bae, Doh C. Lee, and Jaehoon Lim

Subjects
Science
Abstract

Hybrid quantum dot light-emitting diodes exhibit barrier-less carrier injection despite a seemingly unfavourable energy landscape. Here, Lee et al. unravel the origin of this barrier-less carrier injection, showing the critical role of surface states of quantum dots.

Published
2021
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44. Vacuum-field-induced THz transport gap in a carbon nanotube quantum dot

Author

F. Valmorra, K. Yoshida, L. C. Contamin, S. Messelot, S. Massabeau, M. R. Delbecq, M. C. Dartiailh, M. M. Desjardins, T. Cubaynes, Z. Leghtas, K. Hirakawa, J. Tignon, S. Dhillon, S. Balibar, J. Mangeney, A. Cottet, and T. Kontos

Subjects
Science
Abstract

Strong light-matter coupling has been realized at the level of single atoms and photons throughout most of the electromagnetic spectrum, except for the THz range. Here, the authors report a THz-scale transport gap, induced by vacuum fluctuations in carbon nanotube quantum dot through the deep strong coupling of a single electron to a THz resonator.

Published
2021
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45. Silicon: quantum dot photovoltage triodes

Author

Wen Zhou, Li Zheng, Zhijun Ning, Xinhong Cheng, Fang Wang, Kaimin Xu, Rui Xu, Zhongyu Liu, Man Luo, Weida Hu, Huijun Guo, Wenjia Zhou, and Yuehui Yu

Subjects
Science
Abstract

While Silicon is widely used for electronic devices, its band-gap limits its use for infrared detection. Here, Zheng et al present a method for overcoming this limitation, by integrating colloidal quantum dots, with the resulting structure exhibiting high sensitivity to infrared radiation.

Published
2021
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47. The effect of water on colloidal quantum dot solar cells

Author

Shi, Guozheng, Wang, Haibin, Zhang, Yaohong, Cheng, Chen, Zhai, Tianshu, Chen, Botong, Liu, Xinyi, Jono, Ryota, Mao, Xinnan, Liu, Yang, Zhang, Xuliang, Ling, Xufeng, Zhang, Yannan, Meng, Xing, Chen, Yifan, Duhm, Steffen, Zhang, Liang, Li, Tao, Wang, Lu, Xiong, Shiyun, Sagawa, Takashi, Kubo, Takaya, Segawa, Hiroshi, Shen, Qing, Liu, Zeke, and Ma, Wanli

Published
2021
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