Is it permissible to write short supplications (du'as) and remembrances (adhkar) using "الآ" instead of the usual "الألف", and does the ruling differ when writing the Qur'an in this manner?

It is not correct to write the bare alif in this form (آ) because it contains a phonetic and orthographic error. In this form, it is pronounced as an extended hamza, which is an orthographic error, as the maddah is not placed over the maddah alif unless the extended letter is a hamza. This writing is not permissible in the Holy Quran because it alters the pronunciation and differs from the رسم المصحف (Uthmanic script).