Nitrogen acceptor in 2H-polytyp synthetic MoS2 assessed by multifrequency electron spin resonance

Electron spin resonance (ESR) study on 2H-polytype synthetic MoS2 revealed the N acceptor dopants as being characterized by a spectrum of axial symmetry [g(parallel to) = 2.032(2); g(perpendicular to)= 2.270(2)], typical for a hole-type center in MoS2. The N impurities substitute for S sites, with a density of similar to 2.3 x 10(17) cm(-3), which accounts for the overall p-type doping. With respect to measurements for the applied magnetic field directed along the c-axis, the signal consists of a N-14 primary hyperfine triplet of splitting constant A(parallel to) = 14.7 +/- 0.2 G superimposed on a correlated Gaussian single central line of peak-to-peak width Delta B-p(p)= 15.3 +/- 0.5 G, the latter making up only similar to 26% of the total signal intensity. The current work extends on these results through extensive monitoring of the temperature (7) dependence of salient ESR parameters and studying the impact of thermal treatment. ESR signal saturation studies indicate a N acceptor spin-lattice relaxation time T-1 (4.2 K) approximate to 3 x 10(-4) s, notably different from the much smaller As acceptor's T-1 in geological MoS2. Concerning the thermal stability of the dopant, the N acceptor is found to be drastically passivated when exposed to H-2 at similar to 500 degrees C. Yet, subsequent reactivation attempts in vacuum at temperatures up to 740 degrees C appear unsuccessful, urging great caution with conventional forming gas treatments at T greater than or similar to 500 degrees C. Combination of careful K- and Q-band ESR monitoring of the T-dependent signal intensity resulted in the consolidation of the N dopant as a shallow acceptor of activation energy E-a = 45 +/- 7 meV. The consolidated results establish N as a promising candidate for stable covalently bonded p-type doping of MoS2 layers intended for application in novel nanoelectronic devices. Published by the AVS.