Fabrication of Rochelle Salt Thin Film

Abstract

Rochelle salt (NaKC4H4O6·4H2O), also known as potassium sodium tartrate tetrahydrate, is a material with ferroelectricity and piezoelectricity. It had been extensively used in microphones and earpieces. Since the emerging field of low environmental impact technologies, Rochelle salt is widely investigated again. Many researches on Rochelle salt is made by cutting or combining with other materials. But Rochelle salt are made by cutting or combining with other materials is difficult to apply to manufacture a memory. In order to be used in manufacturing a low operating voltage memory, in this research fabrication of Rochelle salt crystal thin film by evaporation solution growth method is reported. Many methods have been tried to grow crystal thin films: adjusting the size of the space, adjusting the growth direction or using different substrate materials. As a result, the length of 30.90 mm Rochelle salt single crystal is successfully grown and various thickness crystal films are fabricated in the limited space. The presence of crystallization structure films are confirmed by the presence of sharp X-ray diffraction (XRD) patterns on the samples. The sample of 2 mm thickness crystal film is single crystal and the samples of thickness less than 0.5mm (no precise measurement of thickness) crystal films are poly crystal by observing the Raman spectra. Atomic Force Microscope(AFM) is used for observing the samples surface morphology, the crystallinity of Rochelle salt on the surface of Si substrate is better than on the surface of glass is obtained. From ferroelectric measurement results, the true ferroelectric properties are not presented, but there is a possibility that Rochelle salt films can be used as a memory device is been seen. Although the process in this work shows the possibility of producing a film with good crystal surface morphology, from experimental results: millimeter-sized single crystal film can be grown and micron-sized single crystal film growth is difficult. We need to further investigate the microscopic arrangement and orientation of Rochelle salt crystals in the future.