Method for making carbon nanotube arrays

A method for making a carbon nanotube array, the method comprising:

• providing a growth substrate having a first growth substrate surface and a second growth substrate surface opposite to the first growth substrate surface, wherein the growth substrate defines a second through hole extending from the first growth substrate surface to the second growth substrate surface;
• depositing a catalyst layer on the first growth substrate surface;
• placing a gas diffusing unit in a chamber comprising a first inlet and a second inlet spaced apart from each other, wherein the gas diffusing unit is a hollow structure and defines a space and a second outlet;
• providing a gas transporting pipe having a first end and a second end opposite to the first end, wherein the second end is in the chamber and connected to the gas diffusing unit, and the first end passes through the second inlet and extends out of the chamber;
• placing the growth substrate on the gas diffusing unit and cover the second outlet, wherein the growth substrate is located between the catalyst layer and the gas diffusing unit;
• supplying a carbon source gas and a protective gas to the chamber from the first inlet, and heating the growth substrate to a first temperature, to grow a carbon nanotube array on the first growth substrate surface, wherein the carbon nanotube array includes a plurality of carbon nanotubes, and each of the plurality of carbon nanotubes has a bottom end;
• and
• stopping supplying the carbon source gas to the chamber, supplying an oxygen containing gas to the gas transporting pipe from the first end and heating the carbon nanotube array to a second temperature, to oxidize the bottom end of each of the plurality of carbon nanotubes.