Determination of Ni Deposition Rates For Composition Regulation of Ni-Mn-Ga Thin Films

Magneto-mechanical properties of Ni-Mn-Ga alloys strongly depend on chemical composition. We study Ni-Mn-Ga thin films. The control of film composition using a single target physical vapor deposition method is limited and may only be manipulated within a few percent by altering the target power used during deposition. However, a sputtering system using multiple targets offers a larger range of chemical diversity by co-depositing elements independently from each sputter gun. A precise knowledge of the deposition rates, as a function of applied power, to a multi-target physical vapor deposition process used to produce Ni-Mn-Ga thin films is essential for accurate tailoring of film thickness and composition. The deposition rate of individual targets (Ni, Mn and Ni-50 at.-% Ga) may be determined by measuring the resulting thickness from a variety of films sputtered at increasing powers for each target. Multiple Ni films were sputtered onto (100) Si at various powers over two hours using an AJA sputtering system and cross-sections of each were prepared in an acrylic epoxy mount. Film thicknesses were measured with scanning electron microscopy and used to determine the deposition rate for the Ni. The deposition rate increased, from 0.087 to 0.144 nm/sec, as the power increased from 50 to 100 W. Determining the deposition rates of all three targets will allow for the precise control of Ni-Mn-Ga composition as a function of applied power to individual guns. Through controlling the deposition rates, we will deposit films with defined composition which yields the desired structural and magnetic properties needed for making thin film magneto-mechanical devices.