Contrasting effects of doping on insulating and metallic states of NdNi1−xMnxO3 thin films

Abstract

We have deposited NdNi1−xMnxO3 (0 ≤ x ≤ 0.10) thin films on SrTiO3 (001), NdGaO3 (001), and YAlO3 (100) substrates and studied the effects of Mn-doping and strain on the charge transport. The majority of charge carriers are holes. Both the in-plane strain and the Mn-doping affect the electrical transport of the films. The metallic state completely vanishes at Mn-doping of x = 0.10. All the films, including x = 0, deposited on SrTiO3 are insulating throughout the temperature range. We find that the resistivity data of all the insulating films fit to two different models, i.e., variable range hopping and Arrhenius equation, in two different temperature regions. The mechanism of charge-transport in the insulating films changes from one type to another and the temperature range of fittings depend on the level of Mn-doping. The results and analyses clearly show that there are contrasting effects of Mn-doping in the metallic and the insulating regions: on one hand, the resistivity increases with increasing Mn-doping in the metallic region; and on the other hand, the hopping/activation of charge carriers get promoted in the insulating region.

Strain-mediated effects of oxygen deficiency and variation in non-Fermi liquid behavior of epitaxial PrNiO3−δ thin films

“…Thus, on one hand oxygen deficiency causes higher resistivity in the metallic region and on the other hand, it causes a considerably low resistivity values in the insulating state. Such contrasting behavior and crossover have been earlier explained in a frame-work of impurity-induced rise in the defect levels in the insulating state and impurity-induced scattering in the metallic state [16,17].…”

“…Some of us have studied the semi-metallic resistive state of NdNiO 3−δ thin films while varying the oxygen and thickness [16]. Towards ultralow thickness, the films with tensile strain may get incomplete oxygen stoichiometry [17][18][19]. Thus, a study comparing the different oxygen stoichiometry in PrNiO 3 films with tensile and compressive strain in optimal thickness regime is pertinent for understanding the impact on electronic transport.…”

Switching of majority charge carriers by Zn doping in NdNiO3 thin films

“…Also, the transition metals like Cu, Fe, Co, are used as the dopant in bulk LaNiO 3 and NdNiO 3 [33][34][35]. However, in thin films, there are only a few studies performed on Nisite doping [19,20,23,36]. In our earlier investigations, the doping of electrons via larger size tetravalent Mn at Ni site under strain (compressive and tensile) was found responsible for shifting the T MI at higher temperatures and bring a complete insulating state [19,23].…”

“…A systematic tuning of T MI has been observed by varying many different parameters in thin films, such as by changing the dimensionality (bulk to 2D and 1D) [18], doping [19][20][21][22][23], varying oxygen content [24][25][26], application of electric field or voltage [27,28], strain and thickness variations [18,29,30]. One of the most controlling methods to tune electronic properties is by injecting charge carriers via doping.…”

“…However, in thin films, there are only a few studies performed on Nisite doping [19,20,23,36]. In our earlier investigations, the doping of electrons via larger size tetravalent Mn at Ni site under strain (compressive and tensile) was found responsible for shifting the T MI at higher temperatures and bring a complete insulating state [19,23]. With the above points in mind, we have studied the effects of hole injection via Zn doping in NdNiO 3 thin and thick films and observed several systematic variations in the electronic properties.…”