Hardness testing of boron nitride (BN) nano-structures formed by ion beam irradiation.

Abstract

Hardness measurements on poly-crystalline hexagonal boron nitride ion implanted samples were carried out using the FM 700 Vickers micro-hardness tester. Previously, it has been shown that the implantation of h BN with different ions structurally deforms the irradiated surface layer to cubic BN nano-particles as revealed by Raman spectroscopy, X ray diffraction and electron microscopy . In the present study, the h BN samples were implanted with 150 keV helium , lithium , boron and neon ions at different ion fluences from 1 by 1014 to 5 by 1016 ions over cm2, while varying the sample temperature from room temperature to 300 degree celcious . Before and after ion implantation, sample characterization was done with Raman spectroscopy and Glancing Incidence X ray diffraction GIXRD and the hardness measurements taken. The Raman measurements of the virgin h BN sample has a characterization peak at 1367 cm 1 due to the sp2 hybridized BN planar bonding and after implantation a broad peak around 1300 cm 1 is observed on all spectra and it indicates a phase change to cubic BN, as reported in detail before. The GIXRD results show two peaks at and on all implanted samples. The peak at is the characteristic silicon diffraction peak which came from the sample holder. The peak at is identified as the 111 peak of c BN from JCPDS database no 35 1365 and Aradi et al. The micro-indentation measurements indicate that hardness increases with ion fluence from un implanted measured value until an optimum value. The Stress, Strain, and Youngs modulus of the implanted were determined from micro indentation measurements.