The benchmark Nikkei index of Tokyo stocks briefly sank over 3 percent Thursday morning to below the 38,000 mark, as exporters took a hit from a sharp drop in the dollar against the yen and tech stocks plunged following a drop in their U.S. counterparts overnight. The Nikkei dipped below 38,000 for the first time since mid-June after the index fell for the sixth straight trading day Wednesday after setting a all-time closing high of 42,224.02 on July 11. Concerns over the earnings outlook grew stronger after disappointing results from some U.S. technology firms overnight and as a stronger yen …