Final answer:
The probability of quantum tunneling increases in a non-linear fashion when the width of a barrier is reduced. Since the original thickness leads to 5% tunneling, reducing the barrier width to 0.12 times the original will cause a much larger percentage to tunnel through, but exact figures require complex calculations outside the scope of this platform.
Step-by-step explanation:
The phenomenon in question is known as quantum tunneling, which is a quantum mechanical effect where particles can pass through a potential barrier that they classically should not have enough energy to overcome. The probability of tunneling is highly sensitive to the width of the barrier. A given percentage of electrons tunneling through the barrier when the barrier is a certain thickness does not linearly scale when the barrier's thickness is changed, due to the exponential dependence of the tunneling probability on the width of the barrier. If 5% of electrons tunnel through the original barrier, reducing the barrier thickness to 0.12 times the original will significantly increase this percentage, but the exact number requires solving the Schrödinger equation with the given parameters.