Department of Biomedical Engineering, University of Houston, Houston, Texas, United States of America.
PLoS One. 2012;7(5):e37440. doi: 10.1371/journal.pone.0037440. Epub 2012 May 31.
Ion Beam Aperture Array Lithography was applied to top-down fabrication of large dense (10(8)-10(9) particles/cm(2)) arrays of uniform micron-scale particles at rates hundreds of times faster than electron beam lithography. In this process, a large array of helium ion beamlets is formed when a stencil mask containing an array of circular openings is illuminated by a broad beam of energetic (5-8 keV) ions, and is used to write arrays of specific repetitive patterns. A commercial 5-micrometer metal mesh was used as a stencil mask; the mesh size was adjusted by shrinking the stencil openings using conformal sputter-deposition of copper. Thermal evaporation from multiple sources was utilized to form magnetic particles of varied size and thickness, including alternating layers of gold and permalloy. Evaporation of permalloy layers in the presence of a magnetic field allowed creation of particles with uniform magnetic properties and pre-determined magnetization direction. The magnetic properties of the resulting particles were characterized by Vibrating Sample Magnetometry. Since the orientation of the particles on the substrate before release into suspension is known, the orientation-dependent magnetic properties of the particles could be determined.
离子束光掩模光刻技术被应用于自上而下的微米级均匀颗粒的大规模高密度（10^8-10^9 个/平方厘米）阵列的制造，其制造速度比电子束光刻快数百倍。在这个过程中，当一个包含圆形开口的光掩模被能量为（5-8 keV）的宽束离子照射时，就会形成一个大的氦离子束阵列，并用于写入特定的重复图案的阵列。商业的 5 微米金属网被用作光掩模；通过使用铜的共形溅射沉积来收缩光掩模开口，从而调整网孔尺寸。从多个源的热蒸发用于形成具有不同尺寸和厚度的磁性颗粒，包括金和坡莫合金的交替层。在磁场存在的情况下蒸发坡莫合金层可以创建具有均匀磁性能和预定磁化方向的颗粒。通过振动样品磁强计对得到的颗粒的磁性进行了表征。由于在释放到悬浮液之前基底上颗粒的取向是已知的，因此可以确定颗粒的取向相关磁性。
