Formation of submicron-size Mn–As blocks on GaAs(100) substrates

MnAs thin films were grown by low-temperature molecular beam epitaxy on semi-insulating GaAs(1 0 0) substrates under varying growth parameters, including the As4/Mn flux ratio and Mn beam equivalent pressure. When the As4/Mn flux ratio was set at 1–1.2, the Mn–As blocks were formed, and an increasing As4/Mn flux ratio resulted in a growth of αMnAs with the growth direction of [1101] and the the mirror-like surface. Under restricted growth conditions, ferromagnetic hexagonal αMnAs layers were first prepared on GaAs(1 0 0) substrates at 250 °C, and orthorhombic Mn3As2 blocks were subsequently formed on the MnAs layers.