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Germanium films several micrometers in thickness were electrochemically deposited on silicon wafers for the first time without catalysts and at room temperature from a solution containing Ge species that have been electrochemically dissolved from Ge target. The films were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. SEM images show that the deposited products presented different structures (Flower-like, spheres, and thin films) depending on the current density. XRD reveals that the germanium electrodeposits were of polycrystalline structure and have the preferred crystallographic growth orientation of ( 220). The grown films were deposited with nickel contact electrodes for characterization as Metal semiconductor Metal (MSM) photodiodes. The current-voltage (I-V) measurements showed the ability to efficiently detect both UV and visible photons. The low deposition temperature, the ease of thickness control, and the inherent advantage of spatial selectivity of the electrodeposition process make this method a promising way to selectively grow high-quality germanium for electronic device applications.

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...

Photoluminescence (PL) spectra of the germanium deposited nanostructures grown on silicon (Si) substrate showed a weak UV peaked at 353 nm (∼3.4 eV), violet-blue at 402 nm (∼3.1 eV), and a broad green band emission in the 470-500 nm (∼2.46 eV) range at room temperature when illuminated by 325 nm line laser beam. Electrochemical growth was monitored and evaluated using scanning electron microscopy (SEM), Raman spectroscopy, and PL. SEM images indicated varied current-density-dependent stoichiometry. The origin of the emissions is attributable to GeO 2 defect centers, exciton confined in a quantum well, and to unbridged oxygen hole centers. These results perhaps are an indication that the blue luminescence is correlated with the formation of Ge (or GeO 2 ) nanocrystals. The radiative recombinations of excitons confined in the nanocrystals are assessed with a possibility of contributing to the shift in the peak.

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This work reports on a synthesis of sub micron germanium dioxide (GeO 2 ) on porous silicon (PS) by electrochemical deposition. n-type Si (100) wafer was used to fabricate (PS) using conventional method of electrochemical etching in HF based solution. A GeCl 4 was directly hydrolyzed by hydrogen peroxide to produce pure GeO 2 , and then electrochemically deposited on PS. Followed by palladium (Pd) contact on GeO 2 /PS was achieved by using RF sputtering technique. The grown GeO 2 crystals were characterized using SEM and EDX. I-V characteristics of Pd/ GeO 2 were recorded before and after hydrogen gas exposure as well as with different H 2 concentrations and different applied temperatures. The sensitivity of Pd/ GeO 2 also has been investigated it could be seen to increase significantly with increased hydrogen concentration while it decreased with increase temperature.