Physical chemistry of aluminum oxynitride and its processing

建立了AlN-Al_2O_3系高温反应平衡的实验方法。用四极杆质谱仪和气相色谱成功地测定了与AlN-Al_2O_3-石墨共存的平衡N_2-CO气体组成。在1723K~1899K温度范围内测定了碳热氮化生成氮化铝反应的标准吉布斯能量变化，由此得到了氮化铝的标准吉布斯生成能和298.15 K时氮化铝的第三定律生成热。用同样的方法测定了γ-AlOx-N尖晶石AlON在1908K-2023K温度范围内的热力学稳定性，估算出AlON分解为α-Al_2O_3和AlN的共析温度为1903±4K，并绘制了Al-O-N-C体系的化学势图，从而在蓝宝石上用AlON缓冲剂制备了AlN层。以氮化铝(AlON)为缓冲层，通过蓝宝石的直接氮化外延制备了AlN薄膜作为蓝光/紫外光发射器的新衬底。在蓝宝石衬底上形成的AlN和AlN层具有如下的结晶学关系：(0001)AlN//(111)AlON//(112^-0)α-Al_2O_3。采用ALO缓冲液使蓝宝石衬底与AlN层界面的晶格失配减少近一半，这主要归因于单晶AlN的生长。

The experimental method for the high-temperature reaction equilibria in the AlN-Al_2O_3 system has been established. The equilibrium N_2-CO gas compositions coexisting with AlN-Al_2O_3-graphite have been successfully measured by quadrupole mass spectrometry and gas chromatography. From the obtained results, the standard Gibbs energy change of the forming reaction of AlN by carbothermal nitridation is determined at temperatures ranging from 1723 to 1899 K. From the obtained result, the standard Gibbs energy of formation of AlN and the third-law enthalpy of formation of AlN at 298.15 K are derived. By using the same method, the thermodynamic stability of γ-aluminum oxynitride spinel, alon, has been determined in the temperature range from 1908 K to 2023 K. The eutectoid decomposition temperature of alon into α-Al_2O_3 and AlN has been evaluated to be 1903 ± 4 K, and the chemical potential diagram of the Al-O-N-C system has been constructed to fabricate an AlN layer on sapphire with*alon buffer. AlN films as a new substrate for blue/UV light emitters have been epitaxialy formed by direct nitridation of sapphire using aluminum oxynitride (alon) as a buffer layer. The alon and AlN layers formed on sapphire have the following crystallographic relation, (0001)AlN//(111)alon//(112^^-0)α-Al_2O_3The lattice mismatch of the interface between sapphire substrate and AlN layer has been reduced almost half by using the along buffer, which significantly attributes to the growth of single crystalline AlN.