The present invention relates to a novel provided gallium arsenide substrates as well as the use thereof. The gallium arsenide substrates provided according to the invention exhibit a so far not obtained surface quality, in particular a homogeneity of surface properties, which is detectable by means of optical surface analyzers, by way of example by means of ellipsometric lateral substrate mapping for optical contact-free quantitative characterization.

The present invention is a process for bio synthesis of nano arsenic trioxide defined by its low toxicity, higher bio availability and nano particle size with the aid of buttermilk, goat urine, dolichos biflorous and other plant materials such as ginger, momordica charantia and musa paradisiaca. The invention is carried out in different steps involving purification of crude form of arsenic trioxide by boiling it with buttermilk, goat urine and extract of dolichos biflorous in subsequent steps, followed by the trituration of the bio purified arsenic trioxide with extracts of ginger and momordica charantia in subsequent steps and heating of the dry product obtained after trituration with musa paradisiaca resulting in the production of novel nano arsenic trioxide. The product is effective in the treatment of various diseases including different types of cancer in animals and humans. The product obtained through the process is less toxic with higher bio availability.

A process for purification of hydrofluoric acid reduces the content of heavy metals, including arsenic, to values lower than five parts per million, without using any chemicals and with an integrated design of hot and cold streams that provide low energy consumption. The process allows extraction of heavy metals, especially arsenic, with minimal waste generation and while maintaining an original oxidation state, which for the case of arsenic is +3, so that the residue can he converted into a product with commercial value, such as arsenious acid. The process includes operation of four systems, namely, a hydrofluoric acid purification system, an arsenic concentration system, a hot water system, and a cold water system. The extraction of heavy metals is performed by synchronized operations of these four systems.

The present invention discloses a polymer-metal compound composite ink, a preparation method and application thereof. The composite ink comprises: at least one polymer; at least one metal compound material, the metal compound material being selected from polyoxometalate compounds and nanocrystalline metal oxides; at least one solvent which is used for forming a disperse system in the form of a uniform fluid together with the remaining components in the composite ink. The present invention also discloses a method for preparing the composite ink. The composite ink of the present invention is easily available in raw material, easy to prepare and low in cost, and can be manufactured into a composite thin film by spin-coating, printing or in other ways. The composite thin film, as an electrode modification layer, can be applied to photoelectric devices such as solar cells or light-emitting diodes, so as to improve the contact performance between an electrode and an organic active layer and thus enhance the performance and yield of photoelectric devices.

A gallium arsenide substrate which exhibits at least one surface having a surface oxide layer comprising gallium and arsenic oxides and which exhibits at least one surface having, according to an ellipsometric lateral substrate mapping with an optical surface analyzer, based on a substrate diameter of 150 mm as reference, a defect number of <6000 and/or a total defect area of less than 2 cm.sup.2, wherein a defect is defined as a continuous area of greater than 1000 m.sup.2 having a deviation from the average measurement signal in elipsometric lateral substrate mapping with an optical surface analyzer of at least 0.05%.