Free-standing ZnO nanowire/graphite membranes: time resolved photoluminescence

TOSI, EZEQUIEL; VEGA, NADIA CELESTE; MARIN-RAMIREZ, OSCAR; GRINBLAT, GUSTAVO; COMEDI, DAVID MARIO

Maceió

Congreso; XXI B-MRS Meeting; 2023

Brazilian Materials Research Society (B-MRS)

ZnO nanowires (NWs) are being studied due to their promising applications in e.g.photonics, optoelectronics, solar cells, sensors and actuators. A few years ago, free standingmembranes consisting of entangled ZnO NWs were developed by some of the authors onseed-free compacted graphite flakes [1]. The excellent UV emission of this hybrid materialas probed by photoluminescence (PL) experiments and their free-standing nature gave clearindication that these membranes are very interesting for several technological applications.However, the origin of such large UV emission remained an open question. In this work, westudy the emission of free standing ZnO/graphite membranes through time resolved andtemperature dependent PL measurements. The samples were fabricated by vapor transportat high temperature in a tubular furnace under controlled (Ar+O2) atmosphere. The NWsgrew on catalyst-free graphite flakes that had been mechanically compacted within analumina boat crucible. The self-supported membranes detached from the crucible base byexfoliation of the graphite substrate following thermal contraction during cooling. The PLtime decay was analyzed in terms of decaying functions and time constants. A long lifetimecomponent in a biexponential PL decay was inferred, which seems to be behind the large UVemissions detected at room temperature. Temperature dependent PL measurements revealrelatively low contributions from nonradiative recombination channels at room temperature,and a fine structure due to complexes emitting in the UV. The overall analysis indicates alow density of nonradiative recombination centers resulting from low precursor velocitiesachieved through a special geometry used during the vapor transport synthesis.Acknowledgements: PICT2019-03795 (FONCyT, Agencia I+D+I), PIP970 and PUE08(CONICET).References:[1] E. Tosi, O. Marin, M. Tirado, D. Comedi, Materials Letters vol. 269, 127658 (2020).