posted on 2014-05-13, 00:00authored byRyan Atkins, Michelle Dolgos, Andreas Fiedler, Corinna Grosse, Saskia
F. Fischer, Sven P. Rudin, David C. Johnson
Four compounds [(SnSe)1.15]m(VSe2)1, where m = 1–4,
were synthesized to explore the effect of increasing the distance
between Se–V–Se dichalcogenide layers on electrical
transport properties. These kinetically stable compounds were prepared
using designed precursors that contained a repeating pattern of elemental
layers with the nanoarchitecture of the desired product. XRD and STEM
data revealed that the precursors self-assembled into the desired
compounds containing a Se–V–Se dichalcogenide layer
precisely separated by a SnSe layer. The 00l diffraction
data are used to determine the position of the Sn, Se, and V planes
along the c-axis, confirming that the average structure
is similar to that observed in the STEM images, and the resulting
data agrees well with results obtained from calculations based on
density functional theory and a semiempirical description of van der
Waals interactions. The in-plane diffraction data contains reflections
that can be indexed as hk0 reflections coming from
the two independent constituents. The SnSe layers diffract independently
from one another and are distorted from the bulk structure to lower
the surface free energy. All of the samples showed metallic-like behavior
in temperature-dependent resistivity between room temperature and
about 150 K. The electrical resistivity systematically increases as m increases. Below 150 K the transport data strongly indicates
a charge density wave transition whose onset temperature systematically
increases as m increases. This suggests increasing
quasi-two-dimensional behavior as increasingly thick layers of SnSe
separate the Se–V–Se layers. This is supported by electronic
structure calculations.