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O. Farinre et al.
Keywords: Tin (IV) oxide · Tin dioxide (SnO 2 ) · Graphene nanoplatelets
(GnPs) · Functionalized GnPs · Scanning electron microscopy (SEM) · Raman
spectroscopy · X-ray diffraction (XRD) · Molecular dynamics (MD) simulation
1 Introduction
1.1 Tin Dioxide (SnO 2 )
Cassiterite or tin (IV) oxide, also known as stannic oxide (SnO 2 ), is an n-type metal oxide
semiconductor material with a large direct band gap of 3.6 eV at room temperature and
elevated electron mobility [1]. It has been used as a photocatalyst, a heat reflector for solar
cells, in lithium ion batteries and optronic devices as electrodes, and most commonly in
gas sensing devices [2]. Gas sensor materials have been increasingly explored to monitor
air quality indoors and in factories and the automotive industry. Much effort has also
been exerted in developing miniature sensors for diagnosing diseases through exhaled
breath analysis [3]. Metal oxide gas sensors in general have high sensitivity and excellent
stability at elevated temperatures in comparison to polymers and metals. However, metal
oxides sensors have low selectivity toward reducing gases and have been customized in
the form of composites and thin films to enhance their selectivity characteristics. Based
on previous studies, pure SnO 2 can detect hydrogen (H 2 ), carbon monoxide (CO), and
methane (CH 4 ) [4]. The tetragonal rutile structure of SnO 2 is the base for technology
due to its stable crystal structure [5]. This crystalline structure of SnO 2 has space-group
symmetry of P4 2 /mnm with point group symmetry D 14
4h and lattice constants a = b =
4.82 Å and c = 3.23 Å [1]. Not too many studies have been conducted regarding the
anharmonic effects of SnO 2 occurring at elevated temperatures, which are crucial to
a better understanding of the thermodynamic stability of SnO 2 and its properties for
thermal transport [6]. In this present study we have characterized SnO 2 by using X-ray
diffraction (XRD) spectroscopy to confirm its tetragonal rutile structure and determine
the associated crystallite size and interplanar distance. We have also recorded the Raman
vibrations at elevated temperatures and observed a red shift with increasing temperatures
for certain Raman active modes. Moreover, Scanning Electron Microscopy (SEM) provided the surface morphology of SnO 2 and helped determine its grain size. Apart from
the experimental work, we have utilized Molecular Dynamics (MD) simulation within
the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) interface
to obtain the lattice constants of SnO 2 and the vibrational properties within the Brillouin
zone.
Fig. 1. Unit cell of SnO 2 containing Sn cations and O anions.
O. Farinre et al.
Keywords: Tin (IV) oxide · Tin dioxide (SnO 2 ) · Graphene nanoplatelets
(GnPs) · Functionalized GnPs · Scanning electron microscopy (SEM) · Raman
spectroscopy · X-ray diffraction (XRD) · Molecular dynamics (MD) simulation
1 Introduction
1.1 Tin Dioxide (SnO 2 )
Cassiterite or tin (IV) oxide, also known as stannic oxide (SnO 2 ), is an n-type metal oxide
semiconductor material with a large direct band gap of 3.6 eV at room temperature and
elevated electron mobility [1]. It has been used as a photocatalyst, a heat reflector for solar
cells, in lithium ion batteries and optronic devices as electrodes, and most commonly in
gas sensing devices [2]. Gas sensor materials have been increasingly explored to monitor
air quality indoors and in factories and the automotive industry. Much effort has also
been exerted in developing miniature sensors for diagnosing diseases through exhaled
breath analysis [3]. Metal oxide gas sensors in general have high sensitivity and excellent
stability at elevated temperatures in comparison to polymers and metals. However, metal
oxides sensors have low selectivity toward reducing gases and have been customized in
the form of composites and thin films to enhance their selectivity characteristics. Based
on previous studies, pure SnO 2 can detect hydrogen (H 2 ), carbon monoxide (CO), and
methane (CH 4 ) [4]. The tetragonal rutile structure of SnO 2 is the base for technology
due to its stable crystal structure [5]. This crystalline structure of SnO 2 has space-group
symmetry of P4 2 /mnm with point group symmetry D 14
4h and lattice constants a = b =
4.82 Å and c = 3.23 Å [1]. Not too many studies have been conducted regarding the
anharmonic effects of SnO 2 occurring at elevated temperatures, which are crucial to
a better understanding of the thermodynamic stability of SnO 2 and its properties for
thermal transport [6]. In this present study we have characterized SnO 2 by using X-ray
diffraction (XRD) spectroscopy to confirm its tetragonal rutile structure and determine
the associated crystallite size and interplanar distance. We have also recorded the Raman
vibrations at elevated temperatures and observed a red shift with increasing temperatures
for certain Raman active modes. Moreover, Scanning Electron Microscopy (SEM) provided the surface morphology of SnO 2 and helped determine its grain size. Apart from
the experimental work, we have utilized Molecular Dynamics (MD) simulation within
the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) interface
to obtain the lattice constants of SnO 2 and the vibrational properties within the Brillouin
zone.
Fig. 1. Unit cell of SnO 2 containing Sn cations and O anions.