Hi , i am interested to know physics behind MOS capacitors, on which iam currently working in . i started to fabriacate a MOS capacitor with out using oxide (silicon dioxide) layer, i have read in articles that a MOS capacitor can be fabricated by using the native oxide layer ( naturally formed ) as an insulator in between the metal contact and semiconductor.i observe a relevant results (similar to MOS capacitor). but i observe that there is no stable characteristics in cv measurents from one sample to other sample.i.e especially near the depletion mode of operation the curve are approaching both towards negative direction of voltage of certain sample and the curves of other sample are approaching in positive direction of voltage.which is undesirable. can i know the reasons affecting the instability in these characteristics and methods to get a stable behaviour. please suggest me the topics along with a good book to be read , in order to understand the physics behind this.