Can a person divorce his wife by giving her a get written on a tablet screen?
No this is not possible. The Rambam (MT Gerushin 4:1) explains why electronic "ink" on a tablet doesn't work
A get may be written only with a substance that leaves a permanent impression - e.g., ink, sikra, kumus, kankantum or the like. If, however, [a get] is written with a substance that does not leave a permanent impression - e.g., beverages, fruit juices or the like - the get is void.
Since the "ink" on a tablet is not permanent, it is not appropriate to write a get.