A method includes forming a semiconductor structure. The structure includes a first material, a blocking material, a second material in an amorphous form, and a third material in an amorphous form. The blocking material is disposed between the first material and the second material. At least the second material and the third material each comprise silicon and/or germanium. The structure is exposed to a temperature above a crystallization temperature of the third material and below a crystallization temperature of the second material. Semiconductor structures, memory devices, and systems are also disclosed.