Spin Polarization and Magnetic Moment in Silicon Carbide Grown by the Method of Coordinated Substitution of Atoms

Abstract

In the present work, a new method for obtaining silicon carbide of the cubic polytype 3C-SiC with silicon vacancies in a stable state is proposed theoretically and implemented experimentally. The idea of the method is that the silicon vacancies are first created by high-temperature annealing in a silicon substrate Si(111) doped with boron B, and only then is this silicon converted into 3C-SiC(111), due to a chemical reaction with carbon monoxide CO. A part of the silicon vacancies that have bypassed “chemical selection” during this transformation get into the SiC. As the process of SiC synthesis proceeds at temperatures of ~1350 °C, thermal fluctuations in the SiC force the carbon atom C adjacent to the vacancy to jump to its place. In this case, an almost flat cluster of four C atoms and an additional void right under it are formed. This stable state of the vacancy, by analogy with NV centers in diamond, is designated as a C4V center. The C4V centers in the grown 3C-SiC were detected experimentally by Raman spectroscopy and spectroscopic ellipsometry. Calculations performed by methods of density-functional theory have revealed that the C4V centers have a magnetic moment equal to the Bohr magneton μB and lead to spin polarization in the SiC if the concentration of C4V centers is sufficiently high.

Dielectric Function and Magnetic Moment of Silicon Carbide Containing Silicon Vacancies

“…As not only V Si but also other defects are formed in this case, the quality of SiC with V Si is not very high upon irradiation. Recently, in the work [9], a much simpler and more reliable method for obtaining silicon vacancies in SiC was proposed and implemented, based on the fact that the formation energy of V Si in silicon Si is much lower (∼3.3 eV) than in SiC. Initially, vacancies are created in Si thermally (i.e., by heating in vacuum to a temperature of T∼1340 ÷ 1380 • C).…”

“…The overall diamond-like bond structure does not change in this case, which makes it possible to obtain high-quality layers of cubic 3C-SiC containing V Si by this method. The concentration of V Si in SiC is determined by the time of preliminary annealing of Si in vacuum [9,12,13]. The longer the annealing, the greater the amount of V Si .…”

“…It is very important to point out that if SiC is grown from Si doped with B, then at temperatures > 1200 • C, a carbon atom C closest to V Si leaps to the place of V Si , which leads to a significant decrease in the total energy [15]. Therewith, four carbon atoms form an almost flat cluster, while a void with a diameter of 2.1 is formed under it at a distance of 1.8 [9]. Without a charge or with a charge of +e, this formation has a magnetic moment equal to the Bohr magneton µ B due to the unpaired p-electron of the C atom located in the center of the cluster at the site of V Si [9].…”

“…Therewith, four carbon atoms form an almost flat cluster, while a void with a diameter of 2.1 is formed under it at a distance of 1.8 [9]. Without a charge or with a charge of +e, this formation has a magnetic moment equal to the Bohr magneton µ B due to the unpaired p-electron of the C atom located in the center of the cluster at the site of V Si [9]. As the magnetic and electrical properties of such a system are very similar to the NV − center in diamond, this formation is named the C 4 V center in the work [9].…”

“…Without a charge or with a charge of +e, this formation has a magnetic moment equal to the Bohr magneton µ B due to the unpaired p-electron of the C atom located in the center of the cluster at the site of V Si [9]. As the magnetic and electrical properties of such a system are very similar to the NV − center in diamond, this formation is named the C 4 V center in the work [9]. If Si is doped with P or Sb, then such a leap of the C atom to the place of V Si is energetically unfavorable due to the received negative charge.…”