David Bosworth | University of Cambridge (original) (raw)
Papers by David Bosworth
AIP Advances, Aug 1, 2015
Amorphous superconductors have become attractive candidate materials for superconducting nanowire... more Amorphous superconductors have become attractive candidate materials for superconducting nanowire single-photon detectors due to their ease of growth, homogeneity and competitive superconducting properties. To date the majority of devices have been fabricated using W x Si 1−x , though other amorphous superconductors such as molybdenum silicide (Mo x Si 1−x) offer increased transition temperature. This study focuses on the properties of MoSi thin films grown by magnetron sputtering. We examine how the composition and growth conditions affect film properties. For 100 nm film thickness, we report that the superconducting transition temperature (Tc) reaches a maximum of 7.6 K at a composition of Mo 83 Si 17. The transition temperature and amorphous character can be improved by cooling of the substrate during growth which inhibits formation of a crystalline phase. X-ray diffraction and transmission electron microscopy studies confirm the absence of long range order. We observe that for a range of 6 common substrates (silicon, thermally oxidized silicon, Rand C-plane sapphire, x-plane lithium niobate and quartz), there is no variation in superconducting transition temperature, making MoSi an excellent candidate material for SNSPDs.
MRS Proceedings, 2012
A variety of characterization techniques have been employed to study the growth and structure of ... more A variety of characterization techniques have been employed to study the growth and structure of nickel carbon thin films fabricated by ionized magnetron sputter deposition. A two target magnetron system is used along with an RF powered coil, to create a secondary plasma, with a DC bias applied at the substrate. By varying the bias it is possible to control the energy of the depositing species as well as a range of other plasma properties and therefore the resulting film microstructure. It has been observed that a change from the metastable hexagonal nickel carbide phase to the stable face centered cubic structure of nickel can be induced. This change in metal crystallinity was accompanied by a change in carbon ordering. The ability to control the film structure and morphology without the need for substrate heating opens up the possibility of depositing a range of structures onto polymers.
No part of this dissertation has been submitted for a degree to any other university. This disser... more No part of this dissertation has been submitted for a degree to any other university. This dissertation is my own work, although some work was done in collaboration with others as specified in the Acknowledgements. The content of this thesis does not exceed 60000 words. I am most grateful for the help and guidance from my supervisor, Dr. Zoe Barber. Her patience and support was invaluable. Special thanks go to Dr. Nadia Stelmashenko, her advice, skill and knowledge in guiding me through the technical aspects of my work were outstanding and this work would not have been possible without her. I would like to thank Mary Vickers and Andrew Moss for their help with the X-ray experiments. For his help with the SEM/EDX work I am greatful to Simon Griggs. I gratefully acknowledge all at the LENNF facility in Leeds but particularly Dr. Michael Ward for the TEM work and Dr. Alex Walton for the XPS work. The SQUID measurements would not have been possible without the guidance of Tony Dennis. I am grateful for the help of Fred Lord, as a Masters student he helped me with the early Raman work. Additionally Algirdas Baskys, a summer student, was of great help with the work on heat treatments.
The journal of physical chemistry. C, Nanomaterials and interfaces, Jan 6, 2016
Nanocomposite thin films comprised of metastable metal carbides in a carbon matrix have a wide va... more Nanocomposite thin films comprised of metastable metal carbides in a carbon matrix have a wide variety of applications ranging from hard coatings to magnetics and energy storage and conversion. While their deposition using nonequilibrium techniques is established, the understanding of the dynamic evolution of such metastable nanocomposites under thermal equilibrium conditions at elevated temperatures during processing and during device operation remains limited. Here, we investigate sputter-deposited nanocomposites of metastable nickel carbide (Ni3C) nanocrystals in an amorphous carbon (a-C) matrix during thermal postdeposition processing via complementary in situ X-ray diffractometry, in situ Raman spectroscopy, and in situ X-ray photoelectron spectroscopy. At low annealing temperatures (300 °C) we observe isothermal Ni3C decomposition into face-centered-cubic Ni and amorphous carbon, however, without changes to the initial finely structured nanocomposite morphology. Only for highe...
Optics express, Jan 27, 2016
We present low temperature nano-optical characterization of a silicon-on-insulator (SOI) waveguid... more We present low temperature nano-optical characterization of a silicon-on-insulator (SOI) waveguide integrated SNSPD. The SNSPD is fabricated from an amorphous Mo<sub>83</sub>Si<sub>17</sub> thin film chosen to give excellent substrate conformity. At 350 mK, the SNSPD exhibits a uniform photoresponse under perpendicular illumination, corresponding to a maximum system detection efficiency of approximately 5% at 1550 nm wavelength. Under these conditions 10 Hz dark count rate and 51 ps full width at half maximum (FWHM) timing jitter is observed.
MRS Proceedings, 2012
ABSTRACTA variety of characterization techniques have been employed to study the growth and struc... more ABSTRACTA variety of characterization techniques have been employed to study the growth and structure of nickel carbon thin films fabricated by ionized magnetron sputter deposition. A two target magnetron system is used along with an RF powered coil, to create a secondary plasma, with a DC bias applied at the substrate. By varying the bias it is possible to control the energy of the depositing species as well as a range of other plasma properties and therefore the resulting film microstructure. It has been observed that a change from the metastable hexagonal nickel carbide phase to the stable face centered cubic structure of nickel can be induced. This change in metal crystallinity was accompanied by a change in carbon ordering. The ability to control the film structure and morphology without the need for substrate heating opens up the possibility of depositing a range of structures onto polymers.
Superconductor Science and Technology, 2017
Thin Solid Films, 2013
Abstract A variety of characterization techniques have been employed to study the growth and stru... more Abstract A variety of characterization techniques have been employed to study the growth and structure of carbon nickel thin films fabricated by ionised magnetron sputter deposition. A two target magnetron system is used along with an RF powered coil to create a secondary plasma, with a DC bias applied at the substrate. By varying the substrate bias it is possible to control the flux and energy of the depositing species and therefore the resulting film microstructure. Films typically consist of nickel-based nano-particles within a carbon matrix. It has been observed that a change between the metastable hexagonal structure of nickel and the stable face centred cubic phase can be induced. This change in metal crystallinity is accompanied by a change in carbon ordering. The ability to control the film structure and morphology without the need for post-deposition heat treatments opens up the possibility of depositing a range of structures onto temperature sensitive substrates such as polymers.
AIP Advances, Aug 1, 2015
Amorphous superconductors have become attractive candidate materials for superconducting nanowire... more Amorphous superconductors have become attractive candidate materials for superconducting nanowire single-photon detectors due to their ease of growth, homogeneity and competitive superconducting properties. To date the majority of devices have been fabricated using W x Si 1−x , though other amorphous superconductors such as molybdenum silicide (Mo x Si 1−x) offer increased transition temperature. This study focuses on the properties of MoSi thin films grown by magnetron sputtering. We examine how the composition and growth conditions affect film properties. For 100 nm film thickness, we report that the superconducting transition temperature (Tc) reaches a maximum of 7.6 K at a composition of Mo 83 Si 17. The transition temperature and amorphous character can be improved by cooling of the substrate during growth which inhibits formation of a crystalline phase. X-ray diffraction and transmission electron microscopy studies confirm the absence of long range order. We observe that for a range of 6 common substrates (silicon, thermally oxidized silicon, Rand C-plane sapphire, x-plane lithium niobate and quartz), there is no variation in superconducting transition temperature, making MoSi an excellent candidate material for SNSPDs.
MRS Proceedings, 2012
A variety of characterization techniques have been employed to study the growth and structure of ... more A variety of characterization techniques have been employed to study the growth and structure of nickel carbon thin films fabricated by ionized magnetron sputter deposition. A two target magnetron system is used along with an RF powered coil, to create a secondary plasma, with a DC bias applied at the substrate. By varying the bias it is possible to control the energy of the depositing species as well as a range of other plasma properties and therefore the resulting film microstructure. It has been observed that a change from the metastable hexagonal nickel carbide phase to the stable face centered cubic structure of nickel can be induced. This change in metal crystallinity was accompanied by a change in carbon ordering. The ability to control the film structure and morphology without the need for substrate heating opens up the possibility of depositing a range of structures onto polymers.
No part of this dissertation has been submitted for a degree to any other university. This disser... more No part of this dissertation has been submitted for a degree to any other university. This dissertation is my own work, although some work was done in collaboration with others as specified in the Acknowledgements. The content of this thesis does not exceed 60000 words. I am most grateful for the help and guidance from my supervisor, Dr. Zoe Barber. Her patience and support was invaluable. Special thanks go to Dr. Nadia Stelmashenko, her advice, skill and knowledge in guiding me through the technical aspects of my work were outstanding and this work would not have been possible without her. I would like to thank Mary Vickers and Andrew Moss for their help with the X-ray experiments. For his help with the SEM/EDX work I am greatful to Simon Griggs. I gratefully acknowledge all at the LENNF facility in Leeds but particularly Dr. Michael Ward for the TEM work and Dr. Alex Walton for the XPS work. The SQUID measurements would not have been possible without the guidance of Tony Dennis. I am grateful for the help of Fred Lord, as a Masters student he helped me with the early Raman work. Additionally Algirdas Baskys, a summer student, was of great help with the work on heat treatments.
The journal of physical chemistry. C, Nanomaterials and interfaces, Jan 6, 2016
Nanocomposite thin films comprised of metastable metal carbides in a carbon matrix have a wide va... more Nanocomposite thin films comprised of metastable metal carbides in a carbon matrix have a wide variety of applications ranging from hard coatings to magnetics and energy storage and conversion. While their deposition using nonequilibrium techniques is established, the understanding of the dynamic evolution of such metastable nanocomposites under thermal equilibrium conditions at elevated temperatures during processing and during device operation remains limited. Here, we investigate sputter-deposited nanocomposites of metastable nickel carbide (Ni3C) nanocrystals in an amorphous carbon (a-C) matrix during thermal postdeposition processing via complementary in situ X-ray diffractometry, in situ Raman spectroscopy, and in situ X-ray photoelectron spectroscopy. At low annealing temperatures (300 °C) we observe isothermal Ni3C decomposition into face-centered-cubic Ni and amorphous carbon, however, without changes to the initial finely structured nanocomposite morphology. Only for highe...
Optics express, Jan 27, 2016
We present low temperature nano-optical characterization of a silicon-on-insulator (SOI) waveguid... more We present low temperature nano-optical characterization of a silicon-on-insulator (SOI) waveguide integrated SNSPD. The SNSPD is fabricated from an amorphous Mo<sub>83</sub>Si<sub>17</sub> thin film chosen to give excellent substrate conformity. At 350 mK, the SNSPD exhibits a uniform photoresponse under perpendicular illumination, corresponding to a maximum system detection efficiency of approximately 5% at 1550 nm wavelength. Under these conditions 10 Hz dark count rate and 51 ps full width at half maximum (FWHM) timing jitter is observed.
MRS Proceedings, 2012
ABSTRACTA variety of characterization techniques have been employed to study the growth and struc... more ABSTRACTA variety of characterization techniques have been employed to study the growth and structure of nickel carbon thin films fabricated by ionized magnetron sputter deposition. A two target magnetron system is used along with an RF powered coil, to create a secondary plasma, with a DC bias applied at the substrate. By varying the bias it is possible to control the energy of the depositing species as well as a range of other plasma properties and therefore the resulting film microstructure. It has been observed that a change from the metastable hexagonal nickel carbide phase to the stable face centered cubic structure of nickel can be induced. This change in metal crystallinity was accompanied by a change in carbon ordering. The ability to control the film structure and morphology without the need for substrate heating opens up the possibility of depositing a range of structures onto polymers.
Superconductor Science and Technology, 2017
Thin Solid Films, 2013
Abstract A variety of characterization techniques have been employed to study the growth and stru... more Abstract A variety of characterization techniques have been employed to study the growth and structure of carbon nickel thin films fabricated by ionised magnetron sputter deposition. A two target magnetron system is used along with an RF powered coil to create a secondary plasma, with a DC bias applied at the substrate. By varying the substrate bias it is possible to control the flux and energy of the depositing species and therefore the resulting film microstructure. Films typically consist of nickel-based nano-particles within a carbon matrix. It has been observed that a change between the metastable hexagonal structure of nickel and the stable face centred cubic phase can be induced. This change in metal crystallinity is accompanied by a change in carbon ordering. The ability to control the film structure and morphology without the need for post-deposition heat treatments opens up the possibility of depositing a range of structures onto temperature sensitive substrates such as polymers.