Thermodynamic Analysis of ZnO Crystal Growth from the Melt

Recently, the efforts in solid-state materials include developing technologies capable of producing ZnO wafers in large dimensions and good quality based device applications. High quality bulk crystals are obtained by growing from high purity the melt. However, the thermochemical properties of ZnO (high melting point and high vapor pressure) make the growth of single crystals difficult. The thermodynamic calculations show that ZnO crystals can be grown from the melt if a suitable dynamic atmosphere composition is used. The oxygen requirement with increasing the temperature can be fulfilled by adding the NO-NO2 gases into the CO2 atmosphere. At ZnO melting point, the oxygen partial pressure of gas mixtures containing CO2-NO-CO-NO2 at Pt = 5 atm reaches to PO2 = 0.29 atm. According to this new thermodynamic result, it would be expected that ZnO crystal could be grown from the melt at lower total pressure comparing to pure CO2.