text: The Deal–Grove model works very well for single-crystal silicon under most conditions.  However, experimental data shows that very thin oxides (less than about 25 nanometres) grow much more quickly in  than the model predicts. In silicon nanostructures (e.g., silicon nanowires) this rapid growth is generally followed by diminishing oxidation kinetics in a process known as self-limiting oxidation, necessitating a modification of the Deal–Grove model.
  If the oxide grown in a particular oxidation step greatly exceeds 25 nm, a simple adjustment accounts for the aberrant growth rate.  The model yields accurate results for thick oxides if, instead of assuming zero initial thickness (or any initial thickness less than 25 nm), we assume that 25 nm of oxide exists before oxidation begins.  However, for oxides near to or thinner than this threshold, more sophisticated models must be used.
  In the 1980s, it became obvious that an update to the Deal-Grove model is necessary to model the aforementioned thin oxides (self-limiting cases). One such approach that more accurately models thin oxides is the Massoud model from 1985 [2]. The Massoud model is analytical and based on parallel oxidation mechanisms. It changes the parameters of the Deal-Grove model to better model the initial oxide growth with the addition of rate-enhancement terms. 
  The Deal-Grove model also fails for polycrystalline silicon ("poly-silicon").  First, the random orientation of the crystal grains makes it difficult to choose a value for the linear rate constant.  Second, oxidant molecules diffuse rapidly along grain boundaries, so that poly-silicon oxidizes more rapidly than single-crystal silicon.
  Dopant atoms strain the silicon lattice, and make it easier for silicon atoms to bond with incoming oxygen.  This effect may be neglected in many cases, but heavily doped silicon oxidizes significantly faster.  The pressure of the ambient gas also affects oxidation rate.