Transfer doping mechanism

The new transfer doping mechanism produces conductive material with a lower density of gap states than phosphorus-doped material of comparable resistivity, where the substitutional dopant always introduces extra defect states. Evidence for the lower density of defects comes from the magnitude of the low energy shoulder in the photoconductivity response spectrum shown in Fig. 14, where the absorption of the layered material at photon energies below 1.4 eV is more than an order of magnitude lower than the phosphorus-doped material of comparable dark resistivity. Furthermore, the photoconductivity of the transfer-doped material is large (10 Q cm ) compared with the photoconductivity achievable in heavily P-doped material under similar illumination. 

Second, a diamond surface with NEA exhibits a novel doping mechanism that relies on the low ionization energy of diamond with NEA. This transfer doping mechanism yields a subsurface hole accumulation layer and a concomitant high surface conductivity (SC) that is discussed in volume 6. Field effect transistors (FETs) based on this kind of SC have been built [33-35], and attempts are being made to exploit the sensitivity of SC in diamond for ion-sensitive electronic devices such as ion-sensitive FETs (ISFETs) [36, 37]. 

Fig. 2 Cartoon illustrating the two doping mechanisms charge transfer from the adsorbates (left) and dopant reaetivation upon adsorption (right).

Results of surface studies of subatomic layers of metals formed on polymer layers (discussed in Section IV.c.2.) have shown clear evidence for chemical interactions between metal and polymer, which range from charge transfer doping for alkali metals and calcium to covalent interactions for aluminum. In this case, the tunneling model is at odds. Research on the charge injection mechanism at the interface between polymer and metals must be continued. 

Figure 6.7 The chemical structure of bis-FPI and its doping mechanism through an anion-induced electron transfer process (top). Schematic representation of the device structure of PSCs with bis-FPI dispersed full-x layers (bottom). Reproduced with permission from ref. 203. Cop)right 2014 The Royal Society of Chemistry.

FIGURE 3.21 (a) Energy transfer mechanisms of phosphorescent dye as a sensitizer and (b) the EL external efficiency of the DCM2 doped devices. (From Baldo, M.A., Thompson, M.E., and Forrest, S.R., Nature, 403, 750, 2000. With permission.)... 

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