Work function of the mixed-valent manganese perovskites

Abstract

We have performed resistivity and work function measurements on a series of samples with Ln0.7D0.3MnO3 composition, where Ln is a lanthanide (La, Pr, or Nd) and D is a nominally divalent ion (Sr, Ca, or Pb). The resistivity measurements are, within some small variation, in agreement with those previously reported for polycrystalline samples of similar composition. The measurement of a work function in air is often difficult to reproduce, mainly owing to the fact that it is a surface probe and can be modified significantly by attachment of contaminants from the atmosphere. Here we have obtained reproducible results that are slightly more stable than the reference metals used in the measurements. This required the introduction of a higher order correction to a common Kelvin probe experimental procedure. Another factor contributing to the high quality of the results is the low carrier density of the conducting oxides. This allows greater penetration of quasistatic electric fields. The work function results here are in overall agreement with previous photoemission work that determined an approximate electron binding energy. We find the best correlation of increased work function is to strain introduced by larger divalent ions and smaller Lanthanide ions. We conclude that the work function is dominated by electrons near the divalent site, and this is interpreted in terms of strain modifying the coulomb energy of the electronic states.

Transport properties of La2/3Sr1/3MnO3/LaAlO3/Pt tunnel junctions

“…19,20 On the other hand, the values obtained for the barrier height, u 0 , are around 0.4 eV, significantly smaller than the value of the corresponding Schottky barrier between LSMO and LAO. The upper limit of the barrier height between LSMO and LAO, i.e., in the Schottky limit, is given by u 0 ¼ W LSMO À / LAO $ 2.4 eV, being W LSMO the work function of LSMO (W LSMO $ 4.9 eV) 29 and / LAO the electron affinity of LAO (/ LAO $2.5 eV). 30 However, this value could be significantly reduced due to the presence of impurities or defects in the LAO barrier and image charge effects.…”

Reversible Resistive Switching and Multilevel Recording in La0.7Sr0.3MnO3 Thin Films for Low Cost Nonvolatile Memories

“…Φ LSMO ) 4.9 eV is taken from ref. 54 Importantly, KPM is sensitive to different HR states (correct reading and multilevel detection) not distinguishable in the C-SFM measurements. Figure 5c to obtain CPD versus V wr .…”

Thin film deposition of metal oxides in resistance switching devices: electrode material dependence of resistance switching in manganite films

“…In general, PCMO is a p-type semiconductor with a work function of 4.9 eV [40]. Because Ni and Au have a larger work function than PCMO, a Schottky barrier is not expected to be formed between the top electrode and PCMO in the Ni/PCMO/Pt and Au/PCMO/Pt devices.…”