Tuning the electronic effective mass in double-dopedSrTiO3

Abstract

We elucidate the relationship between effective mass and carrier concentration in an oxide semiconductor controlled by a double doping mechanism. In this model oxide system, Sr1−xLaxTiO 3−δ , we can tune the effective mass ranging from 6-20me as a function of filling (carrier concentration) and the scattering mechanism, which are dependent on the chosen lanthanum and oxygen vacancy concentrations. The effective mass values were calculated from the Boltzmann transport equation using the measured transport properties of thin films of Sr1−xLaxTiO 3−δ . We show that the effective mass decreases with carrier concentration in this large band gap, low mobility oxide and this behavior is contrary to the tradional high mobility, small effective mass semiconductors.

Electronic Degeneracy and Intrinsic Magnetic Properties of EpitaxialNb: SrTiO3Thin Films Controlled by Defects

“…As expected, reducing the pressure results in a substantial increase of the c-axis lattice parameter [ Fig. 1(a)] [34]. However, our study adds some important findings to previous works: x-ray analysis shows that the epitaxial films grow fully strained at all pressures [ Fig.…”

Effect of oxygen vacancy distribution on the thermoelectric properties of La-doped SrTiO3 epitaxial thin films

“…52 Hence the validity of the earlier discussion on transport properties of the films based on predominant ionized impurity scattering at temperatures below the Debye temperature is established. From the consistency of the results, it is clear that m* increases with oxygen vacancies demonstrating the prediction by Wunderlich et al 22 and confirming the findings on bulk LSTO by Okuda et al 24 It is to be noted here that the growth conditions of our films are entirely different from what has been reported by Ravichandran et al 23 and hence their observation that m* decreases rapidly and remains nearly constant with increasing carrier concentration is not applicable to our films. The transport properties of the PLD grown STO films depend strongly on cation stoichiometry, which in turn varies with the deposition conditions 53 and hence a more meaningful comparison is not possible.…”

“…With smaller concentration of oxygen vacancies, m* was shown to increase, while an opposite trend was predicted for higher concentrations. By assuming a scattering parameter, r ¼ 1 (scattering by polar optical phonons), Ravichandran et al 23 have deduced m* from Boltzmann transport equation using the measured transport properties of double-doped STO films and concluded that m* decreases with an increase in carrier concentration. For arriving at the results, they have assumed that oxygen vacancies lift the six-fold degeneracy of the conduction band to a four-fold one.…”

Thermoelectric and structural correlations in (Sr1−x−yCaxNSomaily1, Koleśnik2, Dąbrowski3 et al. 2017Phys. Rev. B6040View full textAdd to dashboardCite

“…The theoretical prediction [76] of an inverse relationship between m* and n is therefore not sustained; however, our results are rather consistent with the experimental work reported for La and Nb-doped SrTiO 3 [8,44]. While the effective mass m* of pure SrTiO 3 is relatively high (~ 6-10 m 0 ) [43,79], it is reported that m* values for B-site doped bulk materials can be smaller. For instance, a density-of-states effective mass of 1.9 m 0 for m* is obtained for polycrystalline Nb 5%-SrTiO 3 [80].…”