Study of semiconducting nanomaterials under pressure

Abstract

The pressure induced structural and mechanical properties of nanocrystalline ZnO, ZnS, ZnSe, GaN, CoO, CdSe, CeO(2), SnO(2), SiC, c-BC(2)N, and β-Ga(2)O(3) with different grain sizes have been analyzed under high pressures. The molecular dynamics simulation model has been used to compute isothermal equation of state, volume collapse and bulk modulus of these materials in nano and bulk phases at ambient and high pressures and compared with the experimental data. It is evident from these calculations that the change in particle size affects directly the phase transition pressure and bulk modulus. The values of phase transition pressure and bulk modulus increase with decrease in grain size of the material. The equilibrium cell volume and volume collapse in parent phase is directly proportional to the grain size of the materials. Present results are in good agreement with experimental data. The model is able to explain these thermodynamic properties at varying temperatures and pressures successfully.

Evaluation of Spinodal Pressure for Gallium nitride in the Zinc-blend and Wurtzite Structures by Using Different Equations of State (EOSs)

“…By using different EOSs which satisfy spinodal condition. The spinodal pressure values for GaN obtained in present work is close together with results obtained from works of (Cheng et al, 2008), and (Gupta and Rana, 2012), but differ from that obtained by (Jiuxun, 2005), this may be attributed to the fact that our present work used first principle approach in evaluation of P sp for material obtained within the metastable state, while (jiuxun, 2005) work didn't consider that (Psp) for the material obtained within the metastable state. Present work show that P sp value obtained by Born-Mie EOS is in a good agreement with values given by (Xiaowei et al, 2005) for GaN in zinc-blende structure.…”

“…Present work show that P sp value obtained by Born-Mie EOS is in a good agreement with values given by (Xiaowei et al, 2005) for GaN in zinc-blende structure. While using, either Birch-Muranghan or Bardeen EOS, in the present work, in evaluating P sp value for GaN in wurtzite structure, reveal a good agreement with the values given by (Gupta and Rana, 2012) and (Cheng et al, 2008).…”

High-Pressure Phase Transitions of Morphologically Distinct Zn2SnO4 Nanostructures

“…Over the past few decades, semiconducting nanomaterials of different types and structures have greatly contributed to significant progress in nanoscience and technology due to their salient and flexible opto-electronic, photonic, magnetic, and mechanical features. − As far as the exploration of semiconducting nanomaterials under high pressure is concerned, studies on a variety of materials, namely, the group (IV) elements C, Si, and their compound SiC; group (II–VI) compounds such as ZnS, ZnSe, CdS, CdSe, and CdTe; group (IV–VI) PbS; group (III–V) GaN and AlN; the superhard material, BC 2 N; binary oxides such as TiO 2 , ZnO, SnO 2 , Fe 2 O 3 , and CeO 2 ; the rare-earth oxide, Ho 2 O 3 ; wide band-gap oxides such as β-Ga 2 O 3 and Y 2 O 3 ; p-type compounds including CuO, CoO, and MnS; n-type BaTiO 3 ; and narrow band-gap layered group (V–VI) semiconductors such as Bi 2 Te 3 , have been performed. ,,,,− Most of these studies have shed light on the interesting kinetics of pressure-induced first-order, solid–solid structural transformations, compressibilities, bulk moduli, and stiffness or hardness of the materials. − The thermodynamics of phase transformations and relative stabilities of the phases have also been noted in several studies. − ,− Although there are conflicting trends in the reported transition pressures relating to the Hall–Petch effect that is found as bulk materials are reduced to smaller crystallites, a significant influence from nanosized particles or grains has been commonly suggested as the cause for the dissimilar types of nucleation, growth dynamics, phase transition pathways, and even sequences of the phase transitions or amorphizations of semiconducting materials under high pressure. ,,, A specific size, at which the typical nanoscale effects start to occur in materials, has also been defined as their respective “critical size” in several cases. ,, The contributions of the nanoscale-induced differences in the surface energies of the relevant phases mainly account for the stabilities of the corresponding structures. …”

Controlling the Mechanism of Phase Transformation of Colloidal In2O3 Nanocrystals

“…Similarly, phase can be controlled through the application of pressure, which is a more traditional route employed for bulk materials 40,41 but has more recently been applied to nanoscale systems. 42,43 Temperature is also a critical factor in overcoming energy barriers to phase transformation in both bulk and nanomaterials, 40,44,45 and can be used to alter the mechanism by which the transformation occurs.…”

“…Consequently, the formation of metastable phases is possible below certain NC size. ,, Knowing the critical size at which a phase transformation occurs allows for the preparation of nanomaterials with a well-defined phase via size control. Similarly, phase can be controlled through the application of pressure, which is a more traditional route employed for bulk materials , but has more recently been applied to nanoscale systems. , Temperature is also a critical factor in overcoming energy barriers to phase transformation in both bulk and nanomaterials, ,, and can be used to alter the mechanism by which the transformation occurs.…”