Few electron double quantum dot in an isotopically purified $^{28}$Si   quantum well
  We present a few electron double quantum dot (QD) device defined in an isotopically purified $^{28}$Si quantum well (QW). An electron mobility of $5.5 \cdot 10^4 cm^2(Vs)^{-1}$ is observed in the QW which is the highest mobility ever reported for a 2D electron system in $^{28}$Si. The residual concentration of $^{29}$Si nuclei in the $^{28}$Si QW is lower than $10^{3} ppm$, at the verge where the hyperfine interaction is theoretically no longer expected to dominantly limit the $T_{2}$ spin dephasing time. We also demonstrate a complete suppression of hysteretic gate behavior and charge noise using a negatively biased global top gate. 
Andreas Wild, Johannes Kierig, J\"urgen Sailer, Joel Ager III, Eugene   Haller, Gerhard Abstreiter, Stefan Ludwig, and Domin...
cond-mat.mes-hall cond-mat.mtrl-sci cond-mat.other quant-ph