Nucleic acid sequencing methods and systems, the systems including nanochannel chip including: a nanochannel formed in an upper surface of the nanochannel chip and; a roof covering the nanochannel and comprising nanopores and a field enhancement structure; and a barrier disposed in the nanochannel. The method including: introducing a buffer solution including long-chain nucleic acids to the nanochannel chip; applying a voltage potential across the nanochannel chip to drive the nucleic acids through the nanochannel, towards the barrier, and to translocate the nucleic acids through nanopores adjacent to the barrier, such that bases of each of the nucleic acids pass through the field enhancement structure one base at a time and emerge onto an upper surface of the roof; detecting the Raman spectra of the bases of the nucleic acids as each base passes through the electromagnetic-field enhancement structure; and sequencing the nucleic acids based on the detected Raman spectra.