Synthesis, Structural, and Optical Properties of Electrochemically Deposited GeO[sub 2] on Porous Silicon

Abstract

We present a method to synthesize submicrometer germanium dioxide ͑GeO 2 ͒ on porous silicon ͑PS͒ by electrochemical deposition. The PS was electrochemically prepared in HF based electrolyte. GeCl 4 was directly hydrolyzed by hydrogen peroxide to produce pure GeO 2 and then electrochemically deposited on PS. The scanning electron microscopy results showed that the GeO 2 structures are uniform in shape with diameter ϳ500 nm. The photoluminescence spectrum showed a prominent peak related to GeO 2 at about 400 nm. The results indicated potential applications of GeO 2 on the silicon based substrate for future optoelectronic nanodevices in the visible region using a simple fabrication method.Since the observation of visible luminescence from porous silicon ͑PS͒, 1 nanostructured Si and Ge have attracted much attention. Compared to the vast number of studies on the preparation of Si and Ge quantum dot and nanostructures, 2-6 far fewer reports have addressed the formation of germanium dioxide ͑GeO 2 ͒ nanostructures. The blue luminescent material, GeO 2 , is sought after for optical waveguides and nanoconnection in optoelectronic communication. It is thermally stable and exhibits high dielectric constant, refractive index, and mechanical strength.There have been some studies about GeO 2 nanomaterials, produced by either physical evaporation or thermal oxidation methods. 7 Crystallization through these techniques leads to the formation of one-dimensional ͑1D͒ structures. Hu et al. 8 have synthesized the ␣-GeO 2 nanowires by thermal oxidation of metallic Ge. Su et al. 9 synthesized 1D chain like GeO 2 /ZnGeO 3 structures by thermal oxidation of Ge powder mixed with metallic Zn. More recently, Kim et al. 10 synthesized catalyst-free bulk-quantity GeO 2 nanowires by simply heating Ge powders. More often, GeO 2 nanostructures and mesostructures are synthesized via solution-phase approaches, 11,12 assisted by a metal catalyst. In this article, we reported the synthesis of submicrometer GeO 2 using electrochemical method. First, hydrolyzing GeCl 4 using hydrogen peroxide ͑H 2 O 2 ͒ and followed by electrochemical deposition ͑of GeO 2 ͒ on PS. PS can form a good and stable matrix for GeO 2 besides the advantages of light emission in the visible region as well as increased light absorption or improved gas sensing. Employing the bare silicon ͑Si͒ substrate without metal catalyst will pave the way for integration of future devices with established Si integrated circuit technology resulting in cost effective electrochemical approach to produce high performance products. The microstructural and morphological characteristics of the submicrometer GeO 2 crystals will be discussed in this article. ExperimentalFormation of porous silicon.-Porous silicon was prepared by electrochemical anodization of a quarter of n-type Si͑100͒ wafer ͑2 in. diameter͒ with a resistivity of 1-10 ⍀ cm. Aluminum was deposited by sputtering technique and heated for 4 min at 425°C to form an ohmic contact at the back of the wafer. A home made Teflon cell with a...

An Alternative Method to Grow Ge Thin Films on Si by Electrochemical Deposition for Photonic Applications

“…Furthermore, an additional peak at ∼430 cm −1 can be observed in samples (a, b, and c), which indicates the presence of GeO 2 traces and hence confirms that these deposited Ge structures are not pure Ge. 34 The spectrum of sample (d), deposited at low current density (2.5 mA/cm 2 ), on the other hand illustrates a sharp peak at 300 cm −1 and the absence of the peak associated to GeO 2 (430 cm −1 ). This proves that this sample was a single crystalline structure and more importantly, free of any GeO 2 traces.…”

Electronic Structure of Noncentrosymmetric α-GeO2 with Oxygen Vacancy: Ab Initio Calculations and Comparison with Experiment

“…Germanium dioxide (GeO 2 or germania) has been the focus of many investigations over the recent years because this oxide is a key constituent in optical fibers, microelectronic and microphotonic structures, and luminescence compounds. − In microelectronics, GeO 2 is the important thin-film insulator material for the applications in the Ge-based device structures similar to SiO 2 in the Si-based MOS technology because the germanium oxide layer exists even at high- k oxide/Ge interfaces. ,− Presently, GeO 2 is being intensively explored as a functional dielectric material in memristor devices based on the resistance switching effect. , …”

Nanoporous Silicon as Drug Delivery Systems for Cancer Therapies

“…Nanoporous structures with pore size of less than 100 nm have been fabricated in different materials such as titanium oxide (TiO 2 ), aluminum oxide (Al 2 O 3 ), and silicon (Si) [4,5]. Porous silicon (pSi) has been and still being investigated in both bulk crystalline and as nanostructure for applications as diverse as optics [6][7][8], chemical sensors [9][10][11] and biosensors [12][13][14][15][16], radiotherapy [17], tissue engineering [18], cell culture [19], biotechnology, gas separation, catalyst and microelectronics [20]. pSi with pore size 2-50 nm has played a significant role as a carrier in pharmaceutical technology for its drug loading and controlled release properties [1,2,[21][22][23].…”