Topics: Solid, Crystal, Materials science Pages: 6 (1827 words) Published: March 20, 2013
Catalytic and Non Catalytic Growth of Ga2O3nanostructure over Silicon Substrate Narendra Pandwa-2009PH10727 K Sai Teja Reddy-2009PH10723 Supervisor: Dr. Rajendra Singh Abstract: The available literature and synthesis techniques were reviewed briefly. In the project we present experimental work on the non-catalytic growth of Ga 2O 3 nanowires and their characterization. The major aim was synthesis of Ga2 O3 nanowires along with other nanostructure such as nano-belt, nanoribbon, nano-sheets etc. We tried to analyze the growth factor of nanostructure in a non-catalytic growth of Ga 2 O3 over a silicon substrate. For characterization we employed Scanning Electron Microscopy (SEM), to get the morphological information of grown nanostructure and Energy Dispersive X -ray (EDX) analysis to get elemental information of the grown nanostructure.

INTRODUCTION Nanostructures or nanowires are primitive for nano-science studies and nano technology application. Compared to other low dimension system, nanowires have two quantum confinement directions, while still leaving one unconfined direction for electrical conduction. This allows nanowires to be used in applications where electrical conduction, rather than tunnelling transport is req uired[1]. Nanowires have large surface area, very high density of states, diameter dependent band gap and increased surface scattering for electron and photon which distinguish them from other nanostructures and respective bulk material. Due to resemblance of Al2 O3, β-Ga2O3 was studied thoroughly and in 1970s the conductivity of β-Ga2 O3 was found tobe sensitive to the oxygen concentration of the surrounding atmosphere, which made it good candidate for gas sensing instrument. Since then many synthesis techniques were employed to successfully synthesis Ga2 O3 nanowires like using GaAs powder evaporation, liquid phase precursor method, combustion synthesis, thermal evaporation and arc plasma etc.

but there were little work has been done to investigate how the experimental growth variables affect the nanostructure size, crystallographic structure and morphology. Properties of Ga2O3: Gallium oxide, Ga2O3, is a trivalent metal-oxide semiconductor. Its thermal & chemical stability assures it’s use for many great applications. It’s the only oxide of Ga that is thermodynamically stable in the solid state. Stable from room temperature to it’s melting point (1800 oC). It’s not reactive with acids as strong as HF. It has a monoclinic lattice. It is a n-type wide band gap indirect semiconductor with band gap of 4.4-4.8 eV making it transparent to visible light. It has three luminescent bands – UV, Blue and Green     UV is independent of sample history and is due to recombination of selftrapped exciton Green is due to presence of impurities such as Be, Li, Ge or Sn Blue is due to presence of oxygen vacancies and is observed only in conducting and nomimally undoped Ga2O3 semiconductor Luminescence behaviour is still a matter of controversy[1] β-Ga2O3 is a large band gap semiconductor with an band gap of about 4.4–4.8 eV[1]which shows that it is transparent to visible light. Prepared β-Ga2O3 is generally observed to be of n-type due to slight oxygen deficit,where the oxygen vacancies act as shallow donors with an ionization energy of 0.03-0.04eV[1].At 1000 °C, intrinsic carrier density for synthesized β-Ga2O3is about 1013–1016 cm-3 with carrier mobility of ~10 cm2 V-1 s-1[1]. Crystal Structure of β-Ga2O3: β-Ga2O3 exhibits polymorphism, with five crystalline modifications α, β, γ, δ and ε [1].

It is only β form that is stable from room temperature

up to its melting point of about 1800 °C. Other polymorphs transform to the β form at high temperature as they are meta-stable.β-Ga2O3exhibits monoclinic crystalline structure with unit cell parameters a = 12.23, b = 3.04, c = 5.80and β = 103.7° [1] . Synthesis: Synthesis of β-Ga2O3 nanostructures can be done in 2...
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