NOVELTY - The method comprises supplying a catalyst particle on a semiconductor surface, and forming a carbon nanostructure on the semiconductor surface using the catalyst particle to obtain a carbon nanostructure-functionalized semiconductor surface. The catalyst particle is provided by an electro-deposition or a chemical vapor deposition. The catalyst particle is grown using a growth technique and a carbon gas source such as ethylene. The growth technique uses a hydrogen assistant gas or a nitrogen assistant gas. The carbon nanostructures are 1-100 nm in diameter.    USE - The method is useful for functionalizing a surface of a semiconductor substrate e.g. a stable electrode for a photo-electrochemical sensor, which is useful for back-side illumination of the dense mat and front-side illumination of the sparse and separated layer of carbon nanotubes (all claimed) and for detection, sensing and solar energy conversion.    ADVANTAGE - The method maintains the semiconducting and light generating properties of the substrate surface, improves hydrophobic properties of the surface, protects the surface from oxidation, passivation and decomposition, and avoids negative impact of aqueous molecules on the substrate surface.    DETAILED DESCRIPTION - The method comprises providing a catalyst particle on a semiconductor surface, and forming a carbon nanostructure on the semiconductor surface using the catalyst particle to obtain a carbon nanostructure-functionalized semiconductor surface. The catalyst particle is provided by an electro-deposition or a chemical vapor deposition. The catalyst particle is grown using a growth technique and a carbon gas source such as ethylene. The growth technique uses a hydrogen assistant gas or a nitrogen assistant gas. The carbon nanostructures are 1-100 nm in diameter, and form a hydrophobic protection barrier configured to keep electrolyte and water away from the semiconductor surface. The metallic conduction paths are created through a passivation oxide layer that is disposed on the semiconductor surface. A dense mat of straight and aligned carbon nanotubes is formed, where a density of the carbon nanostructures on the semiconductor surface is 1010-1011 tubes per cm2. A dense mat of curled and twisted carbon nanotubes is formed, and where a density of the carbon nanostructures on the semiconductor surface is 108-1011 tubes per cm2. A sparse and separated layer of carbon nanotubes is formed, where a passivation oxide forms in areas of the semiconductor surface between carbon nanotubes. The catalyst particle are provided by spin coating or drop casting a colloidal solution comprising a metal ion in a solvent on the semiconductor surface, removing the solvent, and performing a sintering process in a reduced atmosphere at a temperature of 600-900 degrees C for less than 1 minute to form the catalyst particles.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a structure of a carbon nanostructure-functionalized semiconductor.