How to use the word 'investigate'

Question

I want to express something like 'I dig further into Quantum Mechanics',which of the following is correct?

1). investigate further into quantum mechanics

2). do a further investigation on quantum mechanics

3). carry out a further investigation on quantum mechanics

4). do a further investigation into quantum mechanics

5). carry out a further investigation into quantum mechanics

Is there any alternative expression that I can use? I want to use as few characters as possible.

Answer 1

I would say

...do [or make] a deeper study of Quantum Mechanics.

"Investigation" sounds more like you're looking into a situation that isn't clear (like a detective would), whereas if you're trying to deepen your knowledge of a well-known field, "study" might be more appropriate.