We investigate the (0001) surface of single crystal quartz with a submonolayer of Rb adsorbates. Using Rydberg atom electromagnetically induced transparency, we investigate the electric fields resulting from Rb adsorbed on the quartz surface, and measure the activation energy of the Rb adsorbates. We show that the adsorbed Rb induces a negative electron affinity (NEA) on the quartz surface. The NEA surface allows low energy electrons to bind to the surface and cancel the electric field from the Rb adsorbates. Our results are important for integrating Rydberg atoms into hybrid quantum systems and the fundamental study of atom-surface interactions, as well as applications for electrons bound to a 2D surface.Due to recent technological advances in fabrication and trapping, hybrid quantum systems (HQS) consisting of atoms and surfaces, as well as electrons and surfaces, are fast emerging as ideal platforms for a diverse range of studies in quantum control, quantum simulation and computing, strongly correlated systems and microscopic probes of surfaces. Miniaturization of chip surfaces is necessary to achieve large platform scalability, but decoherence and noise emerge as serious challenges as feature sizes shrink [1][2][3]. Mitigating the noise is a fundamental and necessary step in realizing the full potential of HQSs for quantum technologies.Combining ultracold Rydberg atoms with surfaces for HQS is attractive because Rydberg atoms can have large sizes, significant electric dipole moments and strong interactions. There have recently been a host of theoretical proposals for utilizing Rydberg atoms near surfaces [4][5][6][7][8]. Progress on the experimental front has been hampered by uncertainties in characterizing interactions of atoms with surfaces, although some recent work in this regards are noteworthy [9][10][11].To take full advantage of Rydberg atom HQSs, a more complete understanding of surfaces is needed. One problem is that Rydberg atoms incident upon metal surfaces can be ionized [12, 13]. A second major hurdle is the background electric fields (Efields) caused by adsorbates [14][15][16][17][18][19]. Rydberg states are sensitive to adsorbate E-fields because they are highly polarizable [20]. Adsorbate E-fields have caused problems for other experiments as well, including Casimir-Polder measurements [21], and surface ion traps [22]. A possible solution is to minimize the E-fields by canceling them out.A convenient surface for applications in HQSs is quartz because of its extensive use in the semiconductor and optics industries. Despite numerous theoretical and experimental studies of bulk SiO 2 [23-25], the surface properties are not well understood. Recent theoretical work has focused on surface reconstruction and the adsorption of water and graphene [26][27][28][29][30]. The (0001) surface has been the subject of recent theoretical interest, partially due to its stability and low surface energy [26,30].In this work, we show that adsorption of Rb atoms on a quartz (SiO 2 (0001)) surface, contrary to prev...