Method for making semiconducting layer

A method for making semiconducting layer comprising:

• providing a carbon nanotube film comprising a plurality of carbon nanotubes;
• providing a conductive substrate and applying an insulating layer on the conductive substrate;
• laying the carbon nanotube film on a surface of the insulating layer, and placing the carbon nanotube film under a scanning electron microscope;
• adjusting the scanning electron microscope with an accelerating voltage ranging from about 5 KV to about 20 KV, a dwelling time ranging from about 6 microseconds to about 20 microseconds and a magnification ranging from about 10000 times to about 100000 times, and taking photos of the carbon nanotube film with the scanning electron microscope;
• obtaining a photo of the carbon nanotube film, wherein the photo shows the plurality of carbon nanotubes and a background, a plurality of first carbon nanotubes of the plurality of carbon nanotubes have lighter color than a color of the background, a plurality of second carbon nanotubes of the plurality of carbon nanotubes have deeper color than the color of the background;
• and
• removing the plurality of first carbon nanotubes.