@article{Lynch2024b,

title = {Gate-Tunable Optical Anisotropy in Wafer-Scale, Aligned Carbon Nanotube Films},

author = {Jason Lynch and Evan Smith and Adam Alfieri and Baokun Song and Matthew Klein and Christopher E. Stevens and Cindy Yueli Chen and Chavez FK. Lawrence and Cherie R. Kagan and Honggang Gu and Shiyuan Liu and Lian-Mao Peng and Shivashankar Vangala and Joshua R. Hendrickson and Deep Jariwala},

doi = {10.1038/s41566-024-01504-0},

year  = {2024},

date = {2024-08-14},

urldate = {2024-08-14},

journal = {Nature Photonics},

abstract = {Telecommunications and polarimetry both require the active control of the polarization of light. Currently, this is done by combining intrinsically anisotropic materials with tunable isotropic materials into heterostructures using complicated fabrication techniques owing to the lack of scalable materials that possess both properties. Tunable birefringent and dichromic materials are scarce and rarely available in high-quality thin films over wafer scales. Here we report semiconducting, highly aligned, single-walled carbon nanotubes (SWCNTs) over 4″ wafers with normalized birefringence and dichroism values of 0.09 and 0.58, respectively. The real and imaginary parts of the refractive index of these SWCNT films are tuned by up to 5.9% and 14.3% in the infrared at 2,200 nm and 1,660 nm, respectively, using electrostatic doping. Our results suggest that aligned SWCNTs are among the most anisotropic and tunable optical materials known and open new avenues for their application in integrated photonics and telecommunications.},

keywords = {carbon nanotubes, gate-tunable refractive index, in-plane anisotropy, nanowires, optical properties, thin films},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {One-pot heat-up synthesis of short-wavelength infrared, colloidal InAs quantum dots},

author = {J Lee and T Zhao and S Yang and M Muduli and CB Murray and CR Kagan},

url = {https://pubs.aip.org/aip/jcp/article/160/7/071103/3266823},

doi = {10.1063/5.0187162},

year  = {2024},

date = {2024-02-21},

urldate = {2024-02-21},

journal = {The Journal of Chemical Physics},

volume = {160},

pages = {071103},

abstract = {III–V colloidal quantum dots (QDs) promise Pb and Hg-free QD compositions with which to build short-wavelength infrared (SWIR) optoelectronic devices. However, their synthesis is limited by the availability of group-V precursors with controllable reactivities to prepare monodisperse, SWIR-absorbing III–V QDs. Here, we report a one-pot heat-up method to synthesize ∼8 nm edge length (∼6.5 nm in height) tetrahedral, SWIR-absorbing InAs QDs by increasing the [In3+]:[As3+] ratio introduced using commercially available InCl3 and AsCl3 precursors and by decreasing the concentration and optimizing the volume of the reducing reagent superhydride to control the concentration of In(0) and As(0) intermediates through QD nucleation and growth. InAs QDs are treated with NOBF4, and their deposited films are exchanged with Na2S to yield n-type InAs QD films. We realize the only colloidal InAs QD photoconductors with responsivity at the technologically important wavelength of 1.55 μm.},

keywords = {colloids, nanocrystal, nanocrystal electronics, optical properties, quantum dots, semiconductors, spectroscopy, surface modification, synthesis, TEM, thin films, transport},

pubstate = {published},

tppubtype = {article}

}

@article{Zhao2022,

title = {Engineering the Surface Chemistry of Colloidal InP Quantum Dots for Charge Transport},

author = {Tianshuo Zhao and Qinghua Zhao and Jaeyoung Lee and Shengsong Yang and Han Wang and Ming-Yuan Chuang and Yulian He and Sarah M. Thompson and Guannan Liu and Nuri Oh and Christopher B. Murray and Cherie R. Kagan},

url = {https://pubs.acs.org/doi/full/10.1021/acs.chemmater.2c01840},

doi = {10.1021/acs.chemmater.2c01840},

year  = {2022},

date = {2022-09-07},

urldate = {2022-09-07},

journal = {Chemistry of Materials},

volume = {34},

issue = {18},

pages = {8306–8315},

abstract = {Colloidal InP quantum dots (QDs) have emerged as potential candidates for constructing nontoxic QD-based optoelectronic devices. However, charge transport in InP QD thin-film assemblies has been limitedly explored. Herein, we report the synthesis of ∼8 nm edge length (∼6.5 nm in height), tetrahedral InP QDs and study charge transport in thin films using the platform of the field-effect transistor (FET). We design a hybrid ligand-exchange strategy that combines solution-based exchange with S2– and solid-state exchange with N3– to enhance interdot coupling and control the n-doping of InP QD films. Further modifying the QD surface with thin, thermally evaporated Se overlayers yields FETs with an average electron mobility of 0.45 cm2 V–1 s–1, ∼10 times that of previously reported devices, and a higher on–off current ratio of 103–104. Analytical measurements suggest lower trap-state densities and longer carrier lifetimes in the Se-modified InP QD films, giving rise to a four-time longer carrier diffusion length.},

keywords = {ligand exchange, ligands, mobility, quantum dots, thin films, transport},

pubstate = {published},

tppubtype = {article}

}

@article{Zhao2021b,

title = {Impurities in Nanocrystal Thin-Film Transistors Fabricated by Cation Exchange},

author = {Qinghua Zhao and Shengsong Yang and Jonah J. Ng and Jun Xu and Yun Chang Choi and Christopher B. Murray and Cherie R. Kagan},

url = {https://doi.org/10.1021/acs.jpclett.1c01551},

doi = {10.1021/acs.jpclett.1c01551},

year  = {2021},

date = {2021-07-09},

urldate = {2021-07-09},

journal = {The Journal of Physical Chemistry Letters},

volume = {12},

number = {28},

pages = {6514–6518},

abstract = {Cation exchange is a versatile tool used to alter the composition of nanostructures and thus to design next-generation catalysts and photonic and electronic devices. However, chemical impurities inherited from the starting materials can degrade device performance. Here, we use a sequential cation-exchange process to convert PbSe into CdSe nanocrystal thin films and study their temperature-dependent electrical properties in the platform of the thin-film transistor. We show that residual Pb impurities have detrimental effects on the device turn-on, hysteresis, and electrical stability, and as the amount increases from 2% to 7%, the activation energy for carrier transport increases from 38(3) to 62(2) meV. Selection and surface functionalization of the transistor’s gate oxide layer and low-temperature atomic-layer deposition encapsulation of the thin-film channel suppress these detrimental effects. By conversion of the nanocrystal thin films layer upon layer, impurities are driven away from the gate–oxide interface and mobilities improve from 3(1) to 32(3) cm2 V–1 s–1.},

keywords = {CdSe, impurities, interfaces, nanocrystal electronics, thin films, transistors, transport},

pubstate = {published},

tppubtype = {article}

}

@article{Goodwin2016,

title = {The effects of inorganic surface treatments on photogenerated carrier mobility and lifetime in PbSe quantum dot thin films},

author = {E.D. Goodwin and Daniel B. Straus and E. Ashley Gaulding and Christopher B. Murray and Cherie R. Kagan},

url = {https://www.sciencedirect.com/science/article/abs/pii/S0301010415002220},

doi = {10.1016/j.chemphys.2015.07.031},

year  = {2016},

date = {2016-06-01},

journal = {Chemical Physics },

volume = {471},

pages = {81-88},

abstract = {We used flash-photolysis, time-resolved microwave conductivity (TRMC) to probe the carrier mobility and lifetime in PbSe quantum dot (QD) thin films treated with solutions of the metal salts of Na2Se and PbCl2. The metal salt treatments tuned the Pb:Se stoichiometry and swept the Fermi energy throughout the QD thin film bandgap. A stoichiometric imbalance favoring excess Se heavily p-doped the QD thin film, shifted the Fermi energy toward the valence band, and yielded the highest TRMC mobility and lifetime. Introducing Pb first compensated the p-doping and shifted the Fermi level through mid-gap, decreasing the TRMC mobility. Further Pb addition created an excess of Pb, n-doped the QD thin film, moved the Fermi level to near the conduction band, and again increased the TRMC mobility. The increase in TRMC mobility as the Fermi energy was shifted toward the band edges by non-stoichiometry is consistent with the QD thin film density of states.},

keywords = {mobility, PbSe, quantum dots, surface modification, thin films, transport},

pubstate = {published},

tppubtype = {article}

}

@article{Gaulding2015,

title = {Deposition of Wafer-Scale Single-Component and Binary Nanocrystal Superlattice Thin Films Via Dip-Coating},

author = {E. Ashley Gaulding and Benjamin T. Diroll and E. D. Goodwin and Zachary J. Vrtis and Cherie R. Kagan and Christopher B. Murray},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.201405575},

doi = {10.1002/adma.201405575},

year  = {2015},

date = {2015-03-27},

journal = {Advanced Materials},

volume = {27},

issue = {18},

pages = {2846-2851},

abstract = {Single-component and binary nanocrystal superlattices are assembled over wafer-scale areas using the dip-coating method. A series of measurements are performed to confirm superlattice assembly. This study demonstrates the versatility of dip-coating in depositing a diverse set of nanocrystal materials and superlattice structures, while combining large-area deposition with nanoscale control.},

keywords = {nanocrystal, superlattices, thin films},

pubstate = {published},

tppubtype = {article}

}

@article{Cativo2014,

title = {Air–Liquid Interfacial Self-Assembly of Conjugated Block Copolymers into Ordered Nanowire Arrays},

author = {Ma. Helen M. Cativo and David K. Kim and Robert A. Riggleman and Kevin G. Yager and Stephen S. Nonnenmann and Huikuan Chao and Dawn A. BonnellvCharles T. Black and Cherie R. Kagan and So-Jung Park},

url = {https://pubs.acs.org/doi/full/10.1021/nn505871b},

doi = {10.1021/nn505871b},

year  = {2014},

date = {2014-12-08},

urldate = {2014-12-08},

journal = {ACS Nano},

volume = {8},

number = {12},

pages = {12755–12762},

abstract = {The ability to control the molecular packing and nanoscale morphology of conjugated polymers is important for many of their applications. Here, we report the fabrication of well-ordered nanoarrays of conjugated polymers, based on the self-assembly of conjugated block copolymers at the air–liquid interface. We demonstrate that the self-assembly of poly(3-hexylthiophene)-block-poly(ethylene glycol) (P3HT-b-PEG) at the air–water interface leads to large-area free-standing films of well-aligned P3HT nanowires. Block copolymers with high P3HT contents (82–91%) formed well-ordered nanoarrays at the interface. The fluidic nature of the interface, block copolymer architecture, and rigid nature of P3HT were necessary for the formation of well-ordered nanostructures. The free-standing films formed at the interface can be readily transferred to arbitrary solid substrates. The P3HT-b-PEG films are integrated in field-effect transistors and show orders of magnitude higher charge carrier mobility than spin-cast films, demonstrating that the air–liquid interfacial self-assembly is an effective thin film fabrication tool for conjugated block copolymers.},

keywords = {copolymers, interfaces, organic compounds, self-assembly, self-organization, thin films},

pubstate = {published},

tppubtype = {article}

}

@article{Diroll2014,

title = {X-ray Mapping of Nanoparticle Superlattice Thin Films},

author = {Benjamin T. Diroll and Vicky V. T. Doan-Nguyen and Matteo Cargnello and E. Ashley Gaulding and Cherie R. Kagan and Christopher B. Murray},

url = {https://pubs.acs.org/doi/full/10.1021/nn5062832},

doi = {10.1021/nn5062832},

year  = {2014},

date = {2014-12-05},

urldate = {2014-12-05},

journal = {ACS Nano},

volume = {8},

number = {12},

pages = {12843–12850},

abstract = {We combine grazing-incidence and transmission small-angle X-ray diffraction with electron microscopy studies to characterize the structure of nanoparticle films with long-range order. Transmission diffraction is used to collect in-plane diffraction data from single grains and locally aligned nanoparticle superlattice films. Systematic mapping of samples can be achieved by translating the sample in front of the X-ray beam with a spot size selected to be on the order of superlattice grain features. This allows a statistical determination of superlattice grain size and size distribution over much larger areas than typically accessible with electron microscopy. Transmission X-ray measurements enables spatial mapping of the grain size, orientation, uniformity, strain, or crystal projections and polymorphs. We expand this methodology to binary nanoparticle superlattice and nanorod superlattice films. This study provides a framework for characterization of nanoparticle superlattices over large areas which complements or expands microstructure information from real-space imaging.},

keywords = {nanocrystal, nanoparticle assembly, superlattices, thin films},

pubstate = {published},

tppubtype = {article}

}

@article{Oh2014,

title = {Engineering Charge Injection and Charge Transport for High Performance PbSe Nanocrystal Thin Film Devices and Circuits},

author = {Soong Ju Oh and Zhuqing Wang and Nathaniel E. Berry and Ji-Hyuk Choi and Tianshuo Zhao and E. Ashley Gaulding and Taejong Paik and Yuming Lai and Christopher B. Murray and Cherie R. Kagan},

url = {https://pubs.acs.org/doi/full/10.1021/nl502491d},

doi = {10.1021/nl502491d},

year  = {2014},

date = {2014-10-09},

journal = {Nano Letters},

volume = {14},

number = {11},

pages = {6210–6216},

abstract = {We study charge injection and transport in PbSe nanocrystal thin films. By engineering the contact metallurgy and nanocrystal ligand exchange chemistry and surface passivation, we demonstrate partial Fermi-level pinning at the metal–nanocrystal interface and an insulator-to-metal transition with increased coupling and doping, allowing us to design high conductivity and mobility PbSe nanocrystal films. We construct complementary nanocrystal circuits from n-type and p-type transistors realized from a single nanocrystal material by selecting the contact metallurgy.},

keywords = {doping, interfaces, ligand exchange, mobility, nanocrystal, nanocrystal electronics, PbSe, surface interactions, surface modification, thin films, transistors, transport},

pubstate = {published},

tppubtype = {article}

}

@article{Diroll2014b,

title = {Synthesis of N-Type Plasmonic Oxide Nanocrystals and the Optical and Electrical Characterization of their Transparent Conducting Films},

author = {Benjamin T. Diroll and Thomas R. Gordon and E. Ashley Gaulding and Dahlia R. Klein and Taejong Paik and Hyeong Jin Yun and E.D. Goodwin and Divij Damodhar and Cherie R. Kagan and Christopher B. Murray},

url = {https://pubs.acs.org/doi/full/10.1021/cm5018823},

doi = {10.1021/cm5018823},

year  = {2014},

date = {2014-07-18},

journal = {Chemistry of Materials},

volume = {26},

number = {15},

pages = {4579–4588},

abstract = {We present a general synthesis for a family of n-type transparent conducting oxide nanocrystals through doping with aliovalent cations. These monodisperse nanocrystals exhibit localized surface plasmon resonances tunable in the mid- and near-infrared with increasing dopant concentration. We employ a battery of electrical measurements to demonstrate that the plasmonic resonance in isolated particles is consistent with the electronic properties of oxide nanocrystal thin films. Hall and Seebeck measurements show that the particles form degenerately doped n-type solids with free electron concentrations in the range of 1019 to 1021 cm–3. These heavily doped oxide nanocrystals are used as the building blocks of conductive, n-type thin films with high visible light transparency.},

keywords = {doping, nanocrystal, nanocrystal electronics, optical properties, plasmonic, thin films},

pubstate = {published},

tppubtype = {article}

}