Advances in processing and nanofabrication have led to higher and higher quality nanomaterials.  Most of these processes have been done by the usage of photolithography and chemical etching.  Photolithography is using light to cause a reaction in a surface to create a shape.  This is then chemically etched to remove a layer of material.  The problem with the use of photolithography in nanotechnology is that the size of the object created can only be as small as the smallest wavelength of light used.  Smaller and smaller wavelengths have been used to create smaller objects.  A barrier has been reached however and alternate methods have to be used to produce smaller results.  the following website will let you know further about the subject:  Nanostructures Website