2023-06-05 13:15:30
Diamond is a material of great technological and scientific interest due to its excellent physical, chemical and structural properties. Among others, diamond crystal is the hardest natural solid, retains its solid properties up to extremely high temperatures, and combines excellent electrical insulation with the highest known thermal conductivity.
More recently, it was discovered that boron-doped diamond can exhibit superconductivity at low temperatures, although much remains unknown about the details of the phenomenon.
Now, researchers from the Center for Microanalysis of Materials (CMAM) of the Autonomous University of Madrid (UAM) and the Institute of Materials Science of Madrid (ICMM, dependent on the Higher Council for Scientific Research (CSIC)), in Spain all these institutions, have studied the effects of boron ion irradiation on diamonds and their thermal recovery, with the aim of exploring the possibility of obtaining superconducting structures.
The study analyzed the severe damage inflicted on diamond crystals when irradiated with accelerated ions up to energies of 9 million electron volts (MeV), and their subsequent recovery by heating the diamonds to 1000 degrees Celsius.
Rafael J. Jiménez Riobóo from ICMM, Andrés Redondo-Cubero from CMAM and their colleagues used high-purity diamond crystals, irradiating them with boron ions in the CMAM accelerator. Subsequently, they studied the consequences at the microscopic level using local Raman spectroscopy maps at the micrometer scale at the ICMM.
Although superconductivity was not achieved in the boron-doped diamond samples in this study, the findings provide valuable insight into the behavior of boron-irradiated diamonds and their potential applications in materials science.
Future research in this field could open new avenues for the development of advanced materials and electronic devices with unique properties and innovative applications.
Artist’s impression of accelerated boron ions traversing the crystalline structure of diamond, generating vacancies and depositing at depth. (Image: Andrés Redondo)
Ion Accelerator and Micrometer Raman Spectroscopy Maps
The CMAM has one of the two ion accelerator centers in Spain. The researchers used the accelerator to fabricate boron-implanted diamond microstructures by selectively directing a microbeam of boron ions with enough energy to penetrate the diamond sample. They then studied these irradiated areas using two-dimensional Raman spectroscopy and photoluminescence mapping at ICMM.
Thus, they found that as boron fluence increases, carbon migrates to interstitial sites outside the implantation pathway and the fraction of amorphous carbon increases within the irradiation pathway. For low fluences, annealing at 1000 degrees Celsius is capable of fully recovering the diamond structure without graphitization, while for higher fluences recovery is important but some disorder remains. For very high fluences, annealing at 1200 degrees is detrimental to the diamond lattice and traces of graphitization appear.
The researchers measured the electrical resistance of a selection of the most representative irradiations in the Low Temperatures Laboratory of the UAM. In no case did they observe the superconducting transition, at least cooling down to about minus 271 degrees Celsius. However, the samples treated at 1000 degrees showed a clear improvement in their electrical conductivity, but this worsened orders of magnitude after the subsequent annealing at 1200 degrees.
The research concludes that an incomplete healing of the diamond lattice and the interstitial location of boron could explain why optimally doped samples do not exhibit superconductivity.
The study is titled “Boron-doped diamond by 9 MeV microbeam implantation: Damage and recovery”. And it has been published in the academic journal Carbon. (Source: UAM)
#superconductivity #borondoped #diamonds