Nuclear Magnetic Resonance of Si29 in Lithium Doped Single Crystal Silicon.
Final technical rept. 1 Jan 71-30 Nov 73,
AIR FORCE AERO PROPULSION LAB WRIGHT-PATTERSON AFB OHIO
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Nuclear spin-lattice relaxation times, were measured for high oxygen content single crystal silicon samples doped with various levels of lithium. The samples were grouped into three major categories according to nominal resistivity values prior to lithium doping the resistivities due to background phosphorus doping were .1 ohm cm, 1 ohm cm and 10 ohm cm. After lithium doping the samples possessed resistivities ranging from .025 ohm cm to 10 ohm cm. The samples were identified according to pre-lithium doping resistivity and nominal lithium doping concentrations. In all there were eighteen subgroups--six for each major category. Nuclear spin-lattice relaxation time measurements over a temperature range T 6 K to 300 K at two frequencies v 6.027 MHz, 8.464 MHz were accomplished for a sample with low phosphorus and high lithium content. The results of these measurements along with corresponding Hall measurements led to the conclusion that paramagnetic centers were present at low temperatures it was tentatively concluded that the centers were neutral lithium-oxygen donors. Nuclear spin-lattice relaxation time versus T measurements at v 6.027 MHz were made on a sample that contained three orders of magnitude higher phosphorus content. The conduction electron concentrations at 300 K for this sample and the one discussed immediately above were within twenty percent of their average. Comparison of the nuclear spin-lattice versus T data for these two samples suggested that the phosphorus donors were paramagnetic and were more effective in relaxing the Si29 nuclei than were the lithium-oxygen donors.
- Solid State Physics