Supplemental Materials for
Tunable metal-insulator transition in Nd1-xYxNiO3 (x=0.3,0.4)
perovskites thin film at near room temperature
Tao Shao1, Zeming Qi1,*，Yuyin Wang1, Yuanyuan Li1, Mei Yang1，Yu Wang2, Guobin Zhang1,
Miao Liu3
1National
Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui,
230029,China
2Shanghai
Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Science,
Shanghai, 201204,China
3
Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley,CA 94720, USA
1. We observed negligible hysteresis (<3K) between heating and cooling curves,
which are much smaller than that of the pure NdNiO3 (~30 K). The presence of
hysteresis in the resistivity-temperature curves is due to the coexistence of metallic
and insulate phase. According to Granados et al.’s viewpoint, a small hysteresis
indicates faster transformation dynamics because of relatively higher transition
temperature.1 However, the relationship between hysteresis and transition temperature
is complicate. For example, W doped VO2 has lower transition temperature but also
smaller hysteresis. In fact, hysteresis is a kinetic process that is related both to the
temperature but also the phase transition barrier height. It is not obvious to assume
that all the phase transitions in RNiO3 have the same barrier height. Therefore, the
transition temperature has no direct relation with the hysteresis. In our Nd1-xYxNiO3
system, defects may also act as the nucleation sites for the phase transition and reduce
the hysteresis.
2. EXAFS data analysis was performed using the Athena and Artemis packages.1
Preedge and postedge backgrounds were subtracted according to the standard
procedures. The extraction of the EXAFS signal  (k ) was weighted by k3 and
1
Fourier transformed to R space (insert in Fig.4). The first peak corresponds to the
Ni-O coordination shell. The second and third peaks can be attributed to the second
nearest Ni-Nd(Y) shell and the third nearest Ni-Ni shell, respectively. To obtain
quantitative results, a nonlinear least-squares routine was carried out based on the
EXAFS equation2
 (k )   S02 N j Fj (k ,  )
j
sin[2k R j   j (k )]
kR
2
j
e
2 R j /  2 2 k 2
e
Where S0 is the many-body amplitude reduction factor, Nj is coordination
number of the j shell. Rj is the corresponding average interatomic distance of the j
shell, σ is the mean-square relative displacement. λ is the photoelectron mean free
path. Fj and Φj are the effective scattering amplitude and phase shift respectively,
which were obtained by calculation using Feff package based on the one-electron real
space full-multiple-scattering theory.3
The fitting result of the nearest Ni-O shell is given in Table S1. It is clear that
more Y atoms induced results in larger disorder in Ni-O shell.
Table S1. Local structure parameters of Ni-O shell for Nd1-xYxNiO3 thin films at
different temperature.
Sample
Coordination
Bond length
numbers(N)
RNi-O (Å)
σ2(Å2)
Nd0.7Y0.3NiO3(300K)
5.6
1.94
0.0059
Nd0.7Y0.3NiO3(570K)
5.5
1.94
0.0039
Nd0.6Y0.4NiO3(300K)
5.5
1.96
0.0081
Nd0.6Y0.4NiO3(570K)
5.4
1.93
0.0068
3. The trend of transition temperature based on the prediction of charge density
wave (CDW) is in good with our experimental result. According to Holstain's CDW
2
model, the CDW potential energy is proportional to the charge disproportionate
between nearest neighbor sites.4 The larger charge disproportionation in x=0.4 sample
increases the CDW potential energy and results in higher transition temperature. On
the other hand, the transition sharpness should become more pronounced when the
CDW potential energy goes to larger magnitude.5 However，in reality, transition
sharpness can be affected by many possible reasons, e.g., thin film growth condition,
the substrate, doping, strain, electric-field, etc.6-10 In our case, we have observed that
the transition sharpness decreases with the increase the Y atoms concentration from
x=0.3 to x=0.4. Similar trend have also been observed in several other solid solution
nickelate systems like Nd1-xEuxO3 11, SmxNd1-xNiO312, as well as W-doped VO2 thin
film.13 It is likely that such discrepancy attributes to the doping-induced
inhomogeneity within the sample, such as the strain relaxation, oxygen deficiency,
2
secondary phase, etc.14 Our EXAFS analysis exhibits that the disorder factor  of
x=0.4 sample, which is 0.0081, is noticeably larger than that of x=0.3 sample (0.0059),
indicating that transition sharpness broadening comes along with structural disorder
within the sample. Therefore, in our case, the dependence of transition sharpness on Y
atom concentration becomes complex and is not influenced by CDW potential energy
solely. The other factors such as the strain relation, oxygen deficiency or secondary
phase should also be considered.14 Hence, charge disproportionation and sample
inhomogeneous are competing with each other on modifying the MIT sharpness.
Reference
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