The Microstructure And Electrical Properties Of Boron And Oxygen Co-Dope Diamond Films

The preparation of low resistivity n-type diamond films is a world wide difficulty. To improve the lattice perfection of oxygen ion implanted diamond, we introduced boron and oxygen into diamond films to prepare B-O co-doped diamond films. Three kinds of B-0 co-doped samples series were prepared by implanting boron and oxygen ions into the intrinsic diamond (BO-series) or by implanting oxygen ion into the diamond films doped with low and high concentration of boron in chemical vapor deposition (LBO-series or HBO-series).The microstructure and electric properties of the B-O co-doped diamond films with different ion dose implantation and annealing temperature were studied.Scan electronic microscopy (SEM) showed that the diamond microcrystallines dominantly display (110) planes in intrinsic diamond, while they dominantly orient along (111) planes after boron-oxygen ion implantation. The root-mean-square roughness of diamond surface decreases with the B-O ion co-doped implantation. The diamond microcrystallines orientation change from (111) planes to (110) planes after implanting oxygen ion into diamond films doped with low concentration boron, while they dominantly orient along (111) planes after annealing The diamond microcrystallines dominantly display (110) planes after implanting oxygen ion into diamond films doped with high concentration boron.The properties of different samples series were characterized by Raman spectroscopy. The results show that the tensile stress (0.6GPa) in intrinsic diamond transforms to compressive one after B-O ion implantation and the full width at half maximum (FWHM) increases. After 1000℃annealing, the stress becomes tensile again and the FWHM decreases. With the dose of oxygen ion increasing the tensile stress of LBO-series diamond films transforms to compressive and the FWHM increases. After annealing, the stress keeps along compressive and FWHM decrease. The results show that the high temperature annealing prefers to more significantly improve the crystalline perfection in the oxygen ion implanted LB diamond films.X-ray photoelectron spectroscopy (XPS) measurements show that the C-O bonds are formed in these samples and the addition of boron ions shortens the C-O bond length. It is also revealed that the fraction of shorter C-O bonds in the LBO series is larger than that in BO series, and the FWHM values of C-O peak in XPS spectrum of LBO series are smaller than those of BO series. These data further confirm that a better crystalline perfection exists in the LBO series.Hall effect measurements indicate that the B-O co-doped diamond with the dose of 10¹¹/10¹⁵ cm^-2 and anneal under 1000℃exhibit n-type conduction. By implanting dose of 10¹⁴cm^-2 oxygen ion into diamond films doped with low concentration boron and annealing under 800℃also exhibit n-type conduction. The HBO sample series exhibit p-type conduction .indicating that high boron concentration is to obtain n-type diamond films.