rockm

Um, not to be negative, but the top shoot looks dead. You might scratch a small portion of its bark with you fingernail. If there is no green tissue, the branch is dead and should be removed down to the next living portion of the trunk.

For what it's worth, trunks do not thicken appreciably under bonsai cultivation. Small bonsai do not become big bonsai. Plants grown for bonsai are grown out in the ground or in very large container (the bigger the area available to a plant's roots, the more it will grow up, out and increase in size) BEFORE they are put in display bonsai pots. Potting a bonsai is the final step in a long process..