Properties Of Nitrogen-doped Cuprous Oxide

Cuprous oxide?Cu₂O?is a direct band gap semiconductor which has a forbidden band gap ofabout 2.0eV.It also has the advantages of high absorption coefficient,Earth-abundance,non-toxicity and stability,etc.It is suitable for photovoltaic devices and photocatalysis.Undoped Cu₂O is a p-type semiconductor with relatively high electrical resistivity and doping is usually used to improve its carrier concentration and reduce resistivity.Nitrogen doping can effectively improve hole density and reduce the resistivity of Cu₂O thin films.In the work about nitrogen-doped Cu₂O,doping was realized by improving the flowrate of nitrogen and fixing the sputtering pressure and other parameters.In addition,there has been no report about the effect of annealing on the electrical and optical properties of nitrogen doped Cu₂O.In this thesis,nitrogen doping was realized by varying the sputtering pressure and fixing other parameters,and the effect of annealing on the electrical and optical properties of Cu₂O was studied.We find that lower sputtering pressure favors nitrogen incorporation into Cu₂O and higher sputtering pressure does not;Nitrogen has 3 states in Cu₂O,namely nitrogen atoms,?-N₂?-N=N-?and?-N₂?N?N?which are 2 types of molecules;Annealing under certain conditions have little effect on the electrical and optical properties of nitrogen-doped Cu2O;After annealing,nitrogen atoms disappear and?-N₂ molecules partially turn into?-N₂ molecules.This thesis has 5 chapters.In chapter 1,the basic principles of solar cells and Cu₂O materials are introduced.In chapter 2,direct current sputtering deposition and the characterization methods are introduced.In chapter 3,we firstly prepared pure phase Cu₂O thin films and pure Cu₂O thin films were annealed in Ar or Ar and N₂atmosphere.It is found that annealing Cu₂O thin films in these two atmosphere environments does not change their composition,and nitrogen does not diffuse into the Cu₂O thin films.Secondly,weprepared nitrogen-doped Cu₂O by fixing other parameters but changing the sputtering pressure,and then studied the influence of different sputtering pressure on the preparation of nitrogen-doped Cu₂O thin films.The experimental results show that lower sputtering pressure is beneficial to nitrogen doping,increasing the holes concentration and reducing the resistivity of the sample.In chapter 4,nitrogen-doped Cu₂O thin films are annealed and the annealing was divide into two groups.The first group is to change the annealing time.The second group is to change the annealing temperature.The experimental results show that annealing at higher temperatures can result in a small amount of Cu in the films.After annealing,atomic nitrogen will disappear and?-N₂?-N=N-?molecules will be partially transformed into?-N₂?N?N?molecules.Annealing does not cause damage to the nitrogen-doped Cu₂O films,nor does it have a significant impact on the optical and electrical properties of Cu₂O films.The summary and innovation point are present in chapter 5.