Periodic Reporting for period 3 - WIREDETECT (High resolution X-ray detectors based on nanowire arrays)
Periodo di rendicontazione: 2022-02-01 al 2023-07-31
In this project we are developing ultra-high resolution X-ray detectors based on semiconductor nanowires, whose spatial resolution will be radically better than the current state of the art. In X-ray detectors the primary X-ray absorption induces a cascade of secondary electrons and photons which are measured at the front or back of the detector, but during the long transport to the point of detection these can spread orthogonally to the optical axis. This limits the resolution in present bulk detectors.
The concept of WIREDETECT is to create a nanostructured detector based on an array of semiconductor nanowires, which will confine and physically prevent spreading of the secondary electrons and photons. In a nanowire array, the pixel size is the diameter of the nanowire, which can be as low as 10 nm, while the nanowires can be as long as the X-ray absorption length. The very high aspect ratio of nanowires allows detectors with simultaneously very high spatial resolution and sensitivity. I will investigate both direct detectors and scintillators, in which the secondary electrons and photons are detected, respectively.
The objective is to create detectors based on arrays of 10 nm-diameter nanowires. Time- and temperature resolved measurements will be used to improve understanding of the X-ray physics in these nanodevices, with strong quantum confinement of electrons and phonons and high surface to volume ratio. I will test the detectors within an imaging project targeting the neural connectome, and compare the nanowire detectors with commercial ones. This novel detector concept could revolutionize high-resolution imaging of samples on the nanoscale, maintaining the unique ability of X-rays to study samples in realistic conditions: DNA within live cells, the strained channel in single operational transistors or individual nanoparticles in a charging battery. High resolution detectors could also be employed in X-ray spectroscopy and diffraction.
The concept of WIREDETECT is to create a nanostructured detector based on an array of semiconductor nanowires, which will confine and physically prevent spreading of the secondary electrons and photons. In a nanowire array, the pixel size is the diameter of the nanowire, which can be as low as 10 nm, while the nanowires can be as long as the X-ray absorption length. The very high aspect ratio of nanowires allows detectors with simultaneously very high spatial resolution and sensitivity. I will investigate both direct detectors and scintillators, in which the secondary electrons and photons are detected, respectively.
The objective is to create detectors based on arrays of 10 nm-diameter nanowires. Time- and temperature resolved measurements will be used to improve understanding of the X-ray physics in these nanodevices, with strong quantum confinement of electrons and phonons and high surface to volume ratio. I will test the detectors within an imaging project targeting the neural connectome, and compare the nanowire detectors with commercial ones. This novel detector concept could revolutionize high-resolution imaging of samples on the nanoscale, maintaining the unique ability of X-rays to study samples in realistic conditions: DNA within live cells, the strained channel in single operational transistors or individual nanoparticles in a charging battery. High resolution detectors could also be employed in X-ray spectroscopy and diffraction.
Most of the work has been devoted to making devices of the two types, direct detectors and scintillators. The direct detector subproject has made steady progress, focusing on the single-nanowire detector. In the end of 2019, we successfully made the first vertical nanowire detector. The device was tested at the NanoMax beamline, MAX IV synchrotron in Lund, Sweden. We demonstrated imaging using the 60 nm-diameter nanowire detector, with by far the best spatial resolution of any X-ray detector. The results were published in Nano Letters in 2020. The subproject is currently working in the second phase, optimization of the single-nanowire device.
The scintillator subproject has also been successful. The first nanowire arrays were grown in 2020 and recently reported in Journal of Physical Chemistry C. These structures will be optimized with respect to efficiency and resolution. In addition, we have done significant work on understanding the basic properties of the CsPbBr3 perovskite material. We have studied the ferroelastic domain dynamics using nanofocused XRD, as reported in ACS Nano, Physical Review Materials and New Journal of Physics.
Finally, a significant amount of time and money has been spent on developing the X-ray detector lab. The original plan was to design a home-built system. However, we instead managed to find a very favourable solution from the supplier Rigaku. They supplied us with an X-ray detector system (xSight), in which their scintillator could be replaced by ours. The emission spectra are measured with a fiber-coupled peltier-cooled USB spectrometer from OceanInsight. This system has been successfully used for measuring the spectra and spatial resolution of perovskite nanowire scintillators during the spring 2021.
The scintillator subproject has also been successful. The first nanowire arrays were grown in 2020 and recently reported in Journal of Physical Chemistry C. These structures will be optimized with respect to efficiency and resolution. In addition, we have done significant work on understanding the basic properties of the CsPbBr3 perovskite material. We have studied the ferroelastic domain dynamics using nanofocused XRD, as reported in ACS Nano, Physical Review Materials and New Journal of Physics.
Finally, a significant amount of time and money has been spent on developing the X-ray detector lab. The original plan was to design a home-built system. However, we instead managed to find a very favourable solution from the supplier Rigaku. They supplied us with an X-ray detector system (xSight), in which their scintillator could be replaced by ours. The emission spectra are measured with a fiber-coupled peltier-cooled USB spectrometer from OceanInsight. This system has been successfully used for measuring the spectra and spatial resolution of perovskite nanowire scintillators during the spring 2021.
- We demonstrated imaging using the 60 nm-diameter nanowire detector, with by far the best spatial resolution of any X-ray detector. The subproject is currently working in the second phase, optimization of the single-nanowire device. One of the goals is to reduce the diameter of the nanowires for even better spatial resolution
- We have made the first single-crystal CsPbBr3 nanowires in AAO
- We have done significant work on understanding the basic properties of the CsPbBr3 perovskite material. We have studied the ferroelastic domain dynamics using nanofocused XRD, as reported in ACS Nano, Physical Review Materials and New Journal of Physics.
- We have made the first single-crystal CsPbBr3 nanowires in AAO
- We have done significant work on understanding the basic properties of the CsPbBr3 perovskite material. We have studied the ferroelastic domain dynamics using nanofocused XRD, as reported in ACS Nano, Physical Review Materials and New Journal of Physics.