Preparation And Performance Of Quaternary MgZnOS Alloy Thin Films Grown By PLD

The structure of lattice?the lattice parameters?the band gap of ZnO are similar with GaN,and ZnO has the larger exciton binding energy?60 meV?,thus ZnO is considered to be the next ideal material of shor-wavelengh device after GaN.However,two difficulties must be solved to realize the application of ZnO in the optoelectronic devices:the energy-band engineering and p-type doping.For energy-band engineering,the replace of isoelectronic anions or cations can modify the ZnO band gap.For the cations,replacing Zn partly to acquire ternary ZnMeO alloys?Me=Mg?Be?Cd etc.?;for the anions,replacing Zn partly to acquire ternary ZnOX alloys?X=S?Se etc.?.As for the radii of Mg2+?0.57 A?is similar to the radii of Zn2+?0.60 A?,and doping Mg in ZnO can widely adjust the energy band structure of ZnO,so it is extensive to research for the Mg dopes in ZnO as the cations replace Zn.In addition,the research shows that S has the highest solubility in the VI A,and ZnOS has valence band bowing while the content of S increase in the thin films,thus it is extensive to research for the S dopes in ZnO as the anions replace O.Based on the the ternary alloy research,our work is the MgZnOS quaternary alloy by codoping the anion and cation ions.Mg and S co-effect can subtly adjust and control the electron energy band structure of ZnO,and to realize the more freely and larger-scale to tailor the electron energy band structure of ZnO.For this thesis,we choose the pulsed laser deposition?PLD?method,the different contents of homemade MgZnOS ceramic as target material,and O2 as the reaction gas to grow quaternary Mg_xZn_1-xO_1-yS_y alloys thin films on the c-plane?a-plane and m-plane sapphire.The main research contents are as follows:No1.We chose the c-plane sapphire as substrate,homemade Mg_0.12Zn_0.88O_0.18S_0.82 ceramic as target material and fixed the oxygen partial pressure at 2.5 Pa to grow quaternary Mg_xZn_1-xO_1-yS_y alloys thin films with different substrate temperature.The crystal structure,the contents,the optical property and the surface appearance results of Mg_xZn_1-xO_1-yS_y alloys thin films which grown with different of the substrate temperature show that the relatively suitable temperature for growing the Mg_xZn_1-xO_1-yS_y alloys thin films is 600-750?,and choose the 700? as the sapphire substrate temperature to growth the oxygen partial pressure Mg_xZn_1-xO_1-yS_y alloys thin films which was combined the result of AFM.Another,whith increase of the temperature,the S content in the films was decrease and Mg content in the films was almost not changed.Next work,fixed the temperature at 700 ? to grow quaternary Mg_xZn_1-xO_1-yS_y alloys thin films at different oxygen partial pressure.Via optimizing the parameters of technology,Mg_xZn_1-xO_1-yS_y alloys thin films are successfully epitaxy growth on c-plan sapphire.The result about crystal structure,the contents,the optical property and the surface appearance results of Mg_xZn_1-xO_1-yS_y alloys thin films showed that:1)The single phase of Mg_xZn_1-xO_1-yS_y alloys thin films are 0<y<0.31?the O rich?and 0.67?y?0.89?the S rich?,while the Mg content is about 0.08;2)Mg and S co-doping in ZnO has enhanced the solubility of S in the Mg_xZn_1-xO_1-yS_y thin films;3)The lattice c parameter increased with the S contents increasing in the thin films,but the lattice a parameter had not changed;4)The band gap value of Mg_xZn_1-xO_1-yS_y thin films is higher than the band gap value of ZnO1-ySy thin films at the same S content in the films.No2.We chose the a-plane sapphire as substrate,homemade Mg_0.26Zn_0.74O_0.30S_0.70 ceramic as target material and fixed the temperature at 750? to grow quaternary Mg_xZn_1-xO_1-yS_y alloys thin films at different oxygen partial pressure.The crystal structure,the contents,the optical property and the surface appearance results of Mg_xZn_1-xO_1-yS_y alloys thin films showed that:1)On the a-plane sapphire substrate,Mg_xZn_1-xO_1-yS_y thin films epitaxy growth with c-axis;2)The quality of Mg_xZn_1-xO_1-yS_y which grown on a-plane sapphire is better than on c-plane sapphire,as the value of RC decreased from 1.4° to 1.1° and Phi decreased from 10° to 4°;3)When oxygen partial pressure on 0-0.18 Pa and 0.95-6.0 Pa,the single-phase Mg_xZn_1-xO_1-yS_y was wurtzite structure,and the Mg content was almost keeped on 0.23 while the S content was 0.56?y?0.70 and 0.01?y?0.37 respectively.4)With the increasing of S contents in the thin films,the lattice c and lattice a parameters were increased.5)With the increasing of S contents in the thin films,the band gap of MgxZni-xO1-ySy alloy thin films decreased first then decreased.No3.We chose the m-plane sapphire as substrate,homemade Mg_0.26Zn_0.74O_0.30S_0.70 ceramic as target material and fixed the temperature at 750? to grow quaternary Mg_xZn_1-xO_1-yS_y alloys thin films at different oxygen partial pressure.The crystal structure,the contents,the optical property and the surface appearance results of Mg_xZn_1-xO_1-yS_y alloys thin films showed that:1)When the oxygen pressure between 0-0.18 Pa,we can grow the single-phase m-Mg_xZn_1-xO_1-yS_y alloys thin films.2)The highest band gap value is 3.7 eV.This study not only offers a new way for ZnO energy gap adjustment,but also provides the first-hand data for quaternary ZnO alloy,while enriched and developed the system of ZnO based materials.