@article{Bhatia2024,

title = {A tale of two transfers: characterizing polydimethylsiloxane viscoelastic stamping and heated poly bis-A carbonate transfer of hexagonal boron nitride},

author = {Pia Bhatia and Trey T. Shin and Kyril Kavetsky and Benjamin N. Sailors and George Siokos and Alexandra Sofia Uy-Tioco and Rachael N. Keneipp and Jordan A. Gusdorff and Lee C. Bassett and Marija Drndić},

url = {https://www.sciencedirect.com/science/article/pii/S0968432824001641#sec0080},

doi = {10.1016/j.micron.2024.103747},

year  = {2024},

date = {2024-11-26},

urldate = {2024-11-26},

journal = {Micron},

volume = {189},

pages = {103747},

abstract = {Two-dimensional (2D) materials have many applications ranging from heterostructure electronics to nanofluidics and quantum technology. In order to effectively utilize 2D materials towards these ends, they must be transferred and integrated into complex device geometries. In this report, we investigate two conventional methods for the transfer of 2D materials: viscoelastic stamping with polydimethylsiloxane (PDMS) and a heated transfer with poly bis-A carbonate (PC). We use both methods to transfer mechanically-exfoliated flakes of hexagonal boron nitride onto silicon nitride (SiNx) substrates and characterize the resulting transfers using atomic force microscopy (AFM), aberration-corrected scanning transmission electron microscopy (AC-STEM) and electron energy loss spectroscopy (EELS). We find that both transfer methods yield flakes with significant and comparable residue (within the limitations of our study on eight samples). Qualitative interpretation of EELS maps demonstrates that this residue is comprised of silicon, carbon and oxygen for both transfer methods. Quantitative analysis of AC-STEM images reveals that the area covered in residue is on average, slightly lower for PDMS transfers (31 % ± 1 %), compared to PC transfers (41 % ± 4 %). This work underscores the importance of improving existing transfer protocols towards applications where cleaner materials are critical, as well as the need for robust methods to clean 2D materials.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Thompson2023,

title = {Red Emission from Copper-Vacancy Color Centers in Zinc Sulfide Colloidal Nanocrystals},

author = {Sarah M. Thompson and Cüneyt Şahin and Shengsong Yang and Michael E. Flatté and Christopher B. Murray and Lee C. Bassett and Cherie R. Kagan},

url = {https://pubs.acs.org/doi/full/10.1021/acsnano.3c00191

https://arxiv.org/abs/2301.04223},

doi = {10.1021/acsnano.3c00191},

year  = {2023},

date = {2023-03-09},

journal = {ACS Nano},

abstract = {Copper-doped zinc sulfide (ZnS:Cu) exhibits down-conversion luminescence in the UV, visible, and IR regions of the electromagnetic spectrum; the visible red, green, and blue emission is referred to as R-Cu, G-Cu, and B-Cu, respectively. The sub-bandgap emission arises from optical transitions between localized electronic states created by point defects, making ZnS:Cu a prolific phosphor material and an intriguing candidate material for quantum information science, where point defects excel as single-photon sources and spin qubits. Colloidal nanocrystals (NCs) of ZnS:Cu are particularly interesting as hosts for the creation, isolation, and measurement of quantum defects, since their size, composition, and surface chemistry can be precisely tailored for bio-sensing and opto-electronic applications. Here, we present a method for synthesizing colloidal ZnS:Cu NCs that emit primarily R-Cu, which has been proposed to arise from the CuZn-VS complex, an impurity-vacancy point defect structure analogous to well-known quantum defects in other materials that produce favorable optical and spin dynamics. First principles calculations confirm the thermodynamic stability and electronic structure of CuZn-VS. Temperature- and time-dependent optical properties of ZnS:Cu NCs show blueshifting luminescence and an anomalous plateau in the intensity dependence as temperature is increased from 19 K to 290 K, for which we propose an empirical dynamical model based on thermally-activated coupling between two manifolds of states inside the ZnS bandgap. Understanding of R-Cu emission dynamics, combined with a controlled synthesis method for obtaining R-Cu centers in colloidal NC hosts, will greatly facilitate the development of CuZn-VS and related complexes as quantum point defects in ZnS.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bhatia2024,

title = {A tale of two transfers: characterizing polydimethylsiloxane viscoelastic stamping and heated poly bis-A carbonate transfer of hexagonal boron nitride},

author = {Pia Bhatia and Trey T. Shin and Kyril Kavetsky and Benjamin N. Sailors and George Siokos and Alexandra Sofia Uy-Tioco and Rachael N. Keneipp and Jordan A. Gusdorff and Lee C. Bassett and Marija Drndić},

url = {https://www.sciencedirect.com/science/article/pii/S0968432824001641#sec0080},

doi = {10.1016/j.micron.2024.103747},

year  = {2024},

date = {2024-11-26},

urldate = {2024-11-26},

journal = {Micron},

volume = {189},

pages = {103747},

abstract = {Two-dimensional (2D) materials have many applications ranging from heterostructure electronics to nanofluidics and quantum technology. In order to effectively utilize 2D materials towards these ends, they must be transferred and integrated into complex device geometries. In this report, we investigate two conventional methods for the transfer of 2D materials: viscoelastic stamping with polydimethylsiloxane (PDMS) and a heated transfer with poly bis-A carbonate (PC). We use both methods to transfer mechanically-exfoliated flakes of hexagonal boron nitride onto silicon nitride (SiNx) substrates and characterize the resulting transfers using atomic force microscopy (AFM), aberration-corrected scanning transmission electron microscopy (AC-STEM) and electron energy loss spectroscopy (EELS). We find that both transfer methods yield flakes with significant and comparable residue (within the limitations of our study on eight samples). Qualitative interpretation of EELS maps demonstrates that this residue is comprised of silicon, carbon and oxygen for both transfer methods. Quantitative analysis of AC-STEM images reveals that the area covered in residue is on average, slightly lower for PDMS transfers (31 % ± 1 %), compared to PC transfers (41 % ± 4 %). This work underscores the importance of improving existing transfer protocols towards applications where cleaner materials are critical, as well as the need for robust methods to clean 2D materials.},

keywords = {2-dimensional systems, Materials Physics, nanocrystals},

pubstate = {published},

tppubtype = {article}

}

@article{Thompson2023,

title = {Red Emission from Copper-Vacancy Color Centers in Zinc Sulfide Colloidal Nanocrystals},

author = {Sarah M. Thompson and Cüneyt Şahin and Shengsong Yang and Michael E. Flatté and Christopher B. Murray and Lee C. Bassett and Cherie R. Kagan},

url = {https://pubs.acs.org/doi/full/10.1021/acsnano.3c00191

https://arxiv.org/abs/2301.04223},

doi = {10.1021/acsnano.3c00191},

year  = {2023},

date = {2023-03-09},

journal = {ACS Nano},

abstract = {Copper-doped zinc sulfide (ZnS:Cu) exhibits down-conversion luminescence in the UV, visible, and IR regions of the electromagnetic spectrum; the visible red, green, and blue emission is referred to as R-Cu, G-Cu, and B-Cu, respectively. The sub-bandgap emission arises from optical transitions between localized electronic states created by point defects, making ZnS:Cu a prolific phosphor material and an intriguing candidate material for quantum information science, where point defects excel as single-photon sources and spin qubits. Colloidal nanocrystals (NCs) of ZnS:Cu are particularly interesting as hosts for the creation, isolation, and measurement of quantum defects, since their size, composition, and surface chemistry can be precisely tailored for bio-sensing and opto-electronic applications. Here, we present a method for synthesizing colloidal ZnS:Cu NCs that emit primarily R-Cu, which has been proposed to arise from the CuZn-VS complex, an impurity-vacancy point defect structure analogous to well-known quantum defects in other materials that produce favorable optical and spin dynamics. First principles calculations confirm the thermodynamic stability and electronic structure of CuZn-VS. Temperature- and time-dependent optical properties of ZnS:Cu NCs show blueshifting luminescence and an anomalous plateau in the intensity dependence as temperature is increased from 19 K to 290 K, for which we propose an empirical dynamical model based on thermally-activated coupling between two manifolds of states inside the ZnS bandgap. Understanding of R-Cu emission dynamics, combined with a controlled synthesis method for obtaining R-Cu centers in colloidal NC hosts, will greatly facilitate the development of CuZn-VS and related complexes as quantum point defects in ZnS.},

keywords = {colloidal nanocrystals, color centers, First-principles calculations, impurity doping, Materials Physics, nanocrystals, photoluminescence, quantum dots, transition metals, ZnS},

pubstate = {published},

tppubtype = {article}

}